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  • Speed/expensive of SQLite query vs. List.contains() for "in-set" icon on list rows

    - by kpdvx
    An application I'm developing requires that the app main a local list of things, let's say books, in a local "library." Users can access their local library of books and search for books using a remote web service. The app will be aware of other users of the app through this web service, and users can browse other users' lists of books in their library. Each book is identified by a unique bookId (represented as an int). When viewing books returned through a search result or when viewing another user's book library, the individual list row cells need to visually represent if the book is in the user's local library or not. A user can have at most 5,000 books in the library, stored in SQLite on the device (and synchronized with the remote web service). My question is, to determine if the book shown in the list row is in the user's library, would it be better to directly ask SQLite (via SELECT COUNT(*)...) or to maintain, in-memory, a List or int[] array of some sort containing the unique bookIds. So, on each row display do I query SQLite or check if the List or int[] array contains the unique bookId? Because the user can have at most 5,000 books, each bookId occupies 4 bytes so at most this would use ~ 20kB. In thinking about this, and in typing this out, it seems obvious to me that it would be far better for performance if I maintained a list or int[] array of in-library bookIds vs. querying SQLite (the only caveat to maintaining an int[] array is that if books are added or removed I'll need to grow or shrink the array by hand, so with this option I'll most likely use an ArrayList or Vector, though I'm not sure of the additional memory overhead of using Integer objects as opposed to primitives). Opinions, thoughts, suggestions?

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  • Confused which joomla module to use

    - by KoolKabin
    hi guys, I am trying to use the ja_nickel template in my site. It can be previewed in: http://www.joomlart.com/demo/#templates.joomlart.com/ja_nickel I am trying to show my latest news in the top information block. It consists of title, thumbnail image and some text. So dun know which one module to use? any idea will be helpful. thank you.

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  • Determine asymmetric latencies in a network

    - by BeeOnRope
    Imagine you have many clustered servers, across many hosts, in a heterogeneous network environment, such that the connections between servers may have wildly varying latencies and bandwidth. You want to build a map of the connections between servers my transferring data between them. Of course, this map may become stale over time as the network topology changes - but lets ignore those complexities for now and assume the network is relatively static. Given the latencies between nodes in this host graph, calculating the bandwidth is a relative simply timing exercise. I'm having more difficulty with the latencies - however. To get round-trip time, it is a simple matter of timing a return-trip ping from the local host to a remote host - both timing events (start, stop) occur on the local host. What if I want one-way times under the assumption that the latency is not equal in both directions? Assuming that the clocks on the various hosts are not precisely synchronized (at least that their error is of the the same magnitude as the latencies involved) - how can I calculate the one-way latency? In a related question - is this asymmetric latency (where a link is quicker in direction than the other) common in practice? For what reasons/hardware configurations? Certainly I'm aware of asymmetric bandwidth scenarios, especially on last-mile consumer links such as DSL and Cable, but I'm not so sure about latency. Added: After considering the comment below, the second portion of the question is probably better off on serverfault.

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  • Implementing a kext that intercepts file system usage.

    - by UraN
    Hi, how do most of antivirus software block file system io in case of an infected file? I suppose all the magic resides in some custom kext to do that. Can anyone point me to some topics on this? Some working example would also be great. I've read apple docs about kext development, but mostly it's all about hardware drivers and i could not find what i need. Thanx.

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  • Unfamiliar Javascript Syntax

    - by user1051643
    Long and short of the story is, whilst reading John Resig's blog (specifically http://ejohn.org/blog/javascript-trie-performance-analysis/) I came across a line which makes absolutely no sense to me whatsoever. Essentially it boils down to object = object[key] = something; (this can be found in the first code block of the article I've linked.) This has proven rather difficult to google, so if anyone can offer some insight / a good online resource for me to learn for myself, I'd much appreciate it.

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  • Drupal: link to latest node of a certain content type

    - by james6848
    I have a link within a block. At the moment it goes to a list of newsletter nodes: <p><a href="<?php global $base_url; print $base_url;?>/news-events/newsletter">Read our latest newsletter</a></p> What I would prefer is to have it go to the latest node of the content type 'newsletter', is this possible?

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  • Exception handling in c#

    - by Lalit
    Hi all, I know how to use try...catch block in c#. Also know why it is using. but what is exact meaning of Exception handling ? see once i write the try {}.. Catch{} i handled null exception then what should happen? what are the standard for exception handling. means what should happen is normally expected if exception occur ?

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  • Can I display twovalues in a Silverlight TextBlock?

    - by Subhen
    Can I data bind two proporties values in a single textblock. For Example some thing like following, though this is noth the correct code: <TextBlock Margin="5" Text="{Binding property1,Binding property2}" Style="{StaticResource Style1}" /> I want to display two values in a single text block . Thanks, Subhendu

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  • Singleton issue causing a buffer overrun

    - by Rudiger
    Hi everyone, Ive created a singleton to store 2 arrays: @interface Globals : NSObject { NSMutableArray *items; NSMutableArray *extras; } + (Globals *)sharedInstance; @property (nonatomic, assign) NSMutableArray *items; @property (nonatomic, assign) NSMutableArray *extras; @end @implementation Globals @synthesize items, extras; + (Globals *)sharedInstance { static Globals *myInstance = nil; @synchronized(self) { if(!myInstance) { myInstance = [[Globals alloc] init]; } } return myInstance; } -(void)dealloc { [items release]; [extras release]; [super dealloc]; } @end When I set the Arrays in the singleton from the App delegate and then output them to NSLog it displays what is expected. But when I call it from a view controller further into the App it displays the first entry fine, some of the second entry and then garbage which is i assume a buffer overrun, sometimes it also crashes. I set the singleton array in the appDelegate like so: Globals *sharedInstance = [Globals sharedInstance]; [sharedInstance setItems:items]; and retrieve it: [[[sharedInstance items] objectAtIndex:indexPath.row] objectForKey:@"name"]; cell.description.text = [[[sharedInstance items] objectAtIndex:indexPath.row] objectForKey:@"description"]; Name works fine in both cells if there is 2, description works in the first case, never in the second case. Is it because the arrays in my singleton aren't static? If so why is it outputting the first entry fine? Cheers for any help.

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  • Create form select from object containing values

    - by marks34
    I have such an object : var options = {1: 'Running', 2: 'Falling', 3: 'Collapsing wall', 4: (...)}; I'd like to create form's select element with ooptions taken from this object, so something like that (code I tried which is not working, but you can get the idea) : html = '<form action="" ><select name="block-action"><option>-------</option>'; for(k in obj){ html += '<option value="'+k+'">'+obj[k]+'</option>' } html += '</select></form>'

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  • Android: Scheduling application to start with repeating alarms not working

    - by vikramagain
    I get my Broadcast receiver to set a recurring alarm, to fire up a service. Unfortunately this does not result in the service being called repeatedly (based on logcat). I've experimented with different values for the time interval too. Can someone help? (I'm testing through Eclipse on Android 3.2 Motorola xoom) Below is the code for the Broadcast receiver. alarm = (AlarmManager) arg0.getSystemService(Context.ALARM_SERVICE); Intent intentUploadService = new Intent (arg0, com.vikramdhunta.UploaderService.class); Calendar calendar = Calendar.getInstance(); calendar.setTimeInMillis(System.currentTimeMillis()); calendar.add(Calendar.SECOND, 3); PendingIntent pi = PendingIntent.getBroadcast(arg0, 0, intentUploadService , 0); alarm.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), 5, pi); Below is the code for the Service class public UploaderService() { super("UploaderService"); mycounterid = globalcounter++; } @Override protected void onHandleIntent(Intent intent) { synchronized(this) { try { for (int i = 1;i < 5;i++) { // doesn't do much right now.. but this should appear in logcat Log.i(TAG,"OK " + globalcounter++ + " uploading..." + System.currentTimeMillis()); } } catch(Exception e) { } } } @Override public void onCreate() { super.onCreate(); Log.d("TAG", "Service created."); } @Override public IBinder onBind(Intent arg0) { return null; } @Override public int onStartCommand(Intent intent, int flags, int startId) { Log.i(TAG, "Starting upload service..." + mycounterid); return super.onStartCommand(intent,flags,startId); }

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  • How can a client gracefully detect when a server disconnects?

    - by Ummar
    I am working on a client-server application. The client continuously reads data from server, so when a server is closed or disconnects then the client crashes. I tried a try/catch block, but it didn't work. My client application is written in C++. I want the client to display some proper message like "Server disconnected," then exit.

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  • Fold C Preprocessor in VIM

    - by Sunny
    Is it possible to fold C preprocessor in VIM. For example: #if defined(DEBUG) //some block of code myfunction(); #endif I want to fold it so that it becomes: +-- 4 lines: #if defined(DEBUG)---

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  • trying to show/hide a div but something is not working

    - by Paul
    window.addEvent('domready', function(){ $('detail_block_table').addEvent('click', function(){ if ($('detail_showDiv').getStyle('display') == 'none') { $('detail_showDiv').setStyle('display','block'); } else { $('detail_showDiv').setStyle('display','none'); } }); }); This is the code, it looks fine but something prevents it from working. Any ideas?

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  • Recover lost code from compiled apk

    - by AlexRamallo
    I have an issue here..and its making me really nervous. I was working on this game, and it was going great, so I took a copy of it on my laptop to work do some work while away from my computer. long story short, hard-drive failure + poor back ups led to me losing a very important class. Is there a way to decompile the apk to retrieve the bit of code that was lost? It isn't overly complicated or sophisticated, its just that its impossible to re-write it without reading every. single. line. of. code. in the entire application since it initializes a LOT of classes and loads a bunch of stuff in a specific way. With a quick google search I was able to find apktool, which decompiles it into a bunch of .smali files, which I don't think were designed for human reading. All I need to recover is one very big method in the class. I found the smali file that contains it and I think I found the line where it starts. something like .method public declared-synchronized load(Lcom/X/X/game/X;)I Anyone help would be appreciated since I would have to scrap the entire game without this method.

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  • HTTP DOM: request.use? Usage?

    - by Jim G.
    I'm looking at the following code block in javascript: var request = new Request(); if(request.Use()) // What exactly does this do? { // ...do stuff } else { // no ajax support? } I've never seen anyone invoke the request.Use() method. My Question: What exactly does request.Use() check? Does it in fact check for AJAX support? Can anyone redirect me to an online API reference?

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  • How to avoid concurrent execution of a time-consuming task without blocking?

    - by Diego V
    I want to efficiently avoid concurrent execution of a time-consuming task in a heavily multi-threaded environment without making threads wait for a lock when another thread is already running the task. Instead, in that scenario, I want them to gracefully fail (i.e. skip its attempt to execute the task) as fast as possible. To illustrate the idea considerer this unsafe (has race condition!) code: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing running = true; try { runExpensiveTask(); } finally { running = false; } } I though about using a variation of Double-Checked Locking (consider that running is a primitive 32-bit field, hence atomic, it could work fine even for Java below 5 without the need of volatile). It could look like this: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing synchronized (ThisClass.class) { if (running) return; running = true; try { runExpensiveTask(); } finally { running = false; } } } Maybe I should also use a local copy of the field as well (not sure now, please tell me). But then I realized that anyway I will end with an inner synchronization block, that still could hold a thread with the right timing at monitor entrance until the original executor leaves the critical section (I know the odds usually are minimal but in this case we are thinking in several threads competing for this long-running resource). So, could you think in a better approach?

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  • How do I ensure jQuery ajax call does not send a local copy of file?

    - by Tommy
    $.ajax({ type: 'GET', url: "string.txt", cache: false, success: function(str){ alert("Data is: "+ str); } }); In this example, string.txt is still sent to the cache (\Temporary Internet Files) How do I ensure that the file is not sent - read from the server only? Am I missing an option? I set cache to false but that does not block it from being sent to client. For example, ajax POST does not send a local copy..... Thanks

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