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• GWT RPC - Does it do enough to protect against CSRF ?

  - by sri

  GWT's RPC mechanism does the following things on every HTTP Request - Sets two custom request headers - X-GWT-Permutation and X-GWT-Module-Base Sets the content-type as text/x-gwt-rpc; charset=utf-8 The HTTP request is always a POST, and on server side GET methods throw an exception (method not supported). Also, if these headers are not set or have the wrong value, the server fails processing with an exception "possibly CSRF?" or something to that effect. Question is : Is this sufficient to prevent CSRF? Is there a way to set custom headers and change content type in a pure cross-site request forgery method?

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• Java/Swing: the fast/slow UI binding problem

  - by Jason S

  I need a way to bind UI indicators to rapidly-changing values. I have a class NumberCruncher which does a bunch of heavy processing in a critical non-UI thread, thousands of iterations of a loop per second, and some number of those result in changes to a set of parameters I care about. (think of them as a key-value store) I want to display those at a slower rate in the UI thread; 10-20Hz would be fine. How can I add MVC-style notification so that my NumberCruncher code doesn't need to know about the UI code/binding?

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• What happens with TCP packets between two Socket.BeginReceive calls?

  - by Rodrigo

  I have a doubt about socket programming. I am developing a TCP packet sniffer. I am using Socket.BeginAccept, Socket.BeginReceive to capture every packet, but when a packet is received I have to process something. It is a fast operation, but would take some milliseconds, and then call BeginReceive again. My question is, what would happen if some packets are sent while I am processing, and haven't called BeginReceive? Are packets lost, or are they buffered internally? Is there a limit?

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• Recordset manipulation in SSIS

  - by JSacksteder

  In my SSIS job, I have a need to accumulate a set of rows and commit them all transitionally when processing has completed successfully. If this was pure SQL, I would use a temp table inside a transaction. In SSIS there are a number of issues complicating this. It's difficult to have multiple components share the same transaction and having temp tables that do not exist at design time is a pain. If I use Recordsets inside SSIS for this purpose, there are other issues. My understanding is that an 'Execute SQL' component will re-initialize the Recordset when it runs, so I can't use that to append an additional row. Is there a way to create an OLE DB connection that references an in-memory Recordset? Is there a better way to achieve this result?

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• Make MySQL database replication always use the most free node?

  - by Chad Johnson

  We started using Multi-Master Replication Manager for MySQL, and I am wondering whether it is possible to to treat this setup like multi-symmetric processing: a process pops off the process queue, and the node (in this case a server) that is most free is selected for the job. It seems that what happens is, the service switches to a slave ONLY when it mysqld crashes or goes away. Is there a way to make database replication for MySQL act in more of a distributed manner? Maybe there is other software besides MMM that can do this? Is there a way to switch the reader role to another server whene mysqld slows down (rather than just when it fails)?

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

  - by user1478598

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

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• In javascript, how do I find out the name of a function from within that function?

  - by roryhewitt

  The title should make it clear. Is it possible from within a function to determine the name of that function? Basically, I'm adding some debugging code to a number of functions, and I'd like to be able to simply add the following line inside every function: if (global_debugOn) alert("Processing function " + function-name); How can I get 'function-name'? Yes, obviously I could simply type in the function name (after all I'm typing in the whole alert bit), but that's a hassle to do, especially if there is a nice simple way of retrieving it dynamically. Plus, as function names change during development, I'd like to keep it up-to-date... I hoped that maybe the arguments attribute might hold this (e.g. arguments[0], like in C), but I couldn't get it to work. I'm not even sure if arguments works anyway. Thanks! Rory

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• iPhone - Get a pointer to the data behind CGDataProvider?

  - by jtrim

  I'm trying to take a CGImage and copy its data into a buffer for later processing. The code below is what I have so far, but there's one thing I don't like about it - it's copying the image data twice. Once for CGDataProviderCopyData() and once for the :getBytes:length call on imgData. I haven't been able to find a way to copy the image data directly into my buffer and cut out the CGDataProviderCopyData() step, but there has to be a way...any pointers? (...pun ftw) NSData *imgData = (NSData *)(CGDataProviderCopyData(CGImageGetDataProvider(myCGImageRef))); CGImageRelease(myCGImageRef); // i've got a previously-defined pointer to an available buffer called "mybuff" [imgData getBytes:mybuff length:[imgData length]];

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• How do I give MacPorts privileges?

  - by cojadate

  I tried to install PostgreSQL server development libraries using MacPorts and got the following: Warning: MacPorts running without privileges. You may be unable to complete certain actions (e.g. install). ---> Computing dependencies for postgresql-server-devel ---> Dependencies to be installed: postgresql-devel ---> Building postgresql-devel Error: Target org.macports.build returned: shell command failed Error: The following dependencies failed to build: postgresql-devel Error: Status 1 encountered during processing. To report a bug, see <http://guide.macports.org/#project.tickets> So I guess that means I need to running MacPorts with privileges and try again. Unfortunately I've no idea how to give MacPorts privileges. I'm running OS X 10.6.3

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• What are the pros and cons of using an in memory DB rather than a ThreadLocal

  - by Pangea

  We have been using ThreadLocal so far to carry some data so as to not clutter the API. However below are some of issues of using thread local that which I don't like: 1) Over the years the data items being carried in thread local has increased 2) Since we started using threads (for some light weight processing), we have also migrating these data to the threads in the pool and copying them back again I am thinking of using an in memory DB for these (we doesn't want to add this to the API). I wondering if this approach is good. What are the pros and cons? thx in advance.

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• What is the fastest collection in c# to implement a prioritizing queue?

  - by Nathan Smith

  I need to implement a queue for messages on a game server so it needs to as fast as possible. The queue will have a maxiumem size. I need to prioritize messages once the queue is full by working backwards and removing a lower priority message (if one exists) before adding the new message. The appliation is asynchronous so access to the queue needs to be locked. I'm currently implementing it using a LinkedList as the underlying storage but have concerns that searching and removing nodes will keep it locked for too long. Heres the basic code I have at the moment: public class ActionQueue { private LinkedList<ClientAction> _actions = new LinkedList<ClientAction>(); private int _maxSize; /// <summary> /// Initializes a new instance of the ActionQueue class. /// </summary> public ActionQueue(int maxSize) { _maxSize = maxSize; } public int Count { get { return _actions.Count; } } public void Enqueue(ClientAction action) { lock (_actions) { if (Count < _maxSize) _actions.AddLast(action); else { LinkedListNode<ClientAction> node = _actions.Last; while (node != null) { if (node.Value.Priority < action.Priority) { _actions.Remove(node); _actions.AddLast(action); break; } } } } } public ClientAction Dequeue() { ClientAction action = null; lock (_actions) { action = _actions.First.Value; _actions.RemoveFirst(); } return action; } }

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• Can't get data with spaces into the database from Ajax POST request

  - by J Jones

  I have a real simple form with a textbox and a button, and my goal is to have an asynchronous request (jQuery: $.ajax) send the text to the server (PHP/mysql a la Joomla) so that it can be added to a database table. Here's the javascript that is sending the data from the client: var value= $('#myvalue').val(); $.ajax( { type: "POST", url: "/administrator/index.php", data: { option: "com_mycomponent", task: "enterValue", thevalue: value, format: "raw"}, dataType: "text", success: reportSavedValue } ); The problem arises when the user enters text with a space in it. The $_POST variable that I receive has all the spaces stripped out, so that if the user enters "This string has spaces", the server gets the value "Thisstringhasspaces". I have been googling around, and have found lots of references that I need to use encodeURIComponent. So I have tried it, but now the value that I get from $_POST is "This20string20has20spaces". So it appears to be encoding it the way I would expect, only to have the percent signs stripped instead of the spaces, and leaving the hex numbers. I'm really confused. It seems that this sort of question is asked and answered everywhere on the web, and everywhere encodeURIComponent is hailed as the silver bullet. But apparently I'm fighting a different breed of lycanthrope. Does anyone have any suggestions?

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• How do you measure latency in low-latency environments?

  - by Ajaxx

  Here's the setup... Your system is receiving a stream of data that contains discrete messages (usually between 32-128 bytes per message). As part of your processing pipeline, each message passes through two physically separate applications which exchange the data using a low-latency approach (such as messaging over UDP) or RDMA and finally to a client via the same mechanism. Assuming you can inject yourself at any level, including wire protocol analysis, what tools and/or techniques would you use to measure the latency of your system. As part of this, I'm assuming that every message that is delivered to the system results in a corresponding (though not equivalent) message being pushed through the system and delivered to the client. The only tool that I've seen on the market like this is TS-Associates TipOff. I'm sure that with the right access you could probably measure the same information using a wire analysis tool (ala wireshark) and the right dissectors, but is this the right approach or are there any commodity solutions that I can use?

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• What are the prerequisites for learning embedded systems programming ?

  - by WarDoGG

  I have completed my graduation in Computer engineering. We had some basic electronics courses in Digital signal processing, Information theory etc but my primary field is Programming. However, i was looking to get into Embedded sytems programming with NO knowledge of how it is done. However, i am very keen on going into this field. My questions : what are the languages used to program embedded system programs ? Will i be able to learn without having any basics in electronics ? any other prerequisites that i should know ?

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• How do I start up an NSRunLoop, and ensure that it has an NSAutoreleasePool that gets emptied?

  - by Nick Forge

  I have a "sync" task that relies on several "sub-tasks", which include asynchronous network operations, but which all require access to a single NSManagedObjectContext. Due to the threading requirements of NSManagedObjectContexts, I need every one of these sub-tasks to execute on the same thread. Due to the amount of processing being done in some of these tasks, I need them to be on a background thread. At the moment, I'm launching a new thread by doing this in my singleton SyncEngine object's -init method: [self performSelectorInBackground:@selector(initializeSyncThread) withObject:nil]; The -initializeSyncThread method looks like this: - (void)initializeSyncThread { self.syncThread = [NSThread currentThread]; self.managedObjectContext = [(MyAppDelegate *)[UIApplication sharedApplication].delegate createManagedObjectContext]; NSRunLoop *runLoop = [NSRunLoop currentRunLoop]; [runLoop run]; } Is this the correct way to start up the NSRunLoop for this thread? Is there a better way to do it? The run loop only needs to handle 'performSelector' sources, and it (and its thread) should be around for the lifetime of the process. When it comes to setting up an NSAutoreleasePool, should I do this by using Run Loop Observers to create the autorelease pool and drain it after every run-through?

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• Limit Connections with semaphores

  - by Robert

  I'm trying to limit the number of connections my server will accept using semaphores, but when running, my code doesn't seem to make this restriction - am I using the semaphore correctly? eg. I have hardcoded the number of permit as 2, but I can connect an unlimited number of clients... public class EServer implements Runnable { private ServerSocket serverSocket; private int numberofConnections = 0; private Semaphore sem = new Semaphore(2); private volatile boolean keepProcessing = true; public EServer(int port) throws IOException { serverSocket = new ServerSocket(port); } @Override public void run() { while (keepProcessing) { try { sem.acquire(); Socket socket = serverSocket.accept(); process(socket, getNextConnectionNumber()); } catch (Exception e) { } finally { sem.release(); } } closeIgnoringException(serverSocket); } private synchronized int getNextConnectionNumber() { return ++numberofConnections; } // processing related methods }

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• IPC speed and compare

  - by Lily

  I am trying to implement a real-time application which involves IPC across different modules. The modules are doing some data intensive processing. I am using message queue as the backbone(Activemq) for IPC in the prototype, which is easy(considering I am a totally IPC newbie), but it's very very slow. Here is my situation: I have isolated the IPC part so that I could change it other ways in future. I have 3 weeks to implement another faster version. ;-( IPC should be fast, but also comparatively easy to pick up I have been looking into different IPC approaches: socket, pipe, shared memory. However, I have no experience in IPC, and there is definitely no way I could fail this demo in 3 weeks... Which IPC will be the safe way to start with? Thanks. Lily

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• Trying to recognize _NSFaultingMutableSet as member of NSSet

  - by Will

  I'm trying to recognize the result of a generic query to a managed object as an NSSet. Currently the class returned is a member of _NSFaultingMutableSet, which is clearly related, but fails the isMemberOf:[NSSet class] and isKindOf:[NSSet class] calls. Given that Cocoa doesn't do a direct implementation of NSSet, it's not surprising that I've got some air in the pipes, but I'm wondering if I'm messing something obvious up or this requires a higher grade of kung-fu than I possess. Code follows: SEL selector = NSSelectorFromString(someString); if(![self respondsToSelector:selector]){ NSLog(@"Error processing item"); return; } id items = [self performSelector:selector]; Class itemsClass = [items class]; if ( [itemsClass isKindOfClass:[NSSet class]]) { // do something }

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• Windows Azure worker roles: One big job or many small jobs?

  - by Ryan Elkins

  Is there any inherent advantage when using multiple workers to process pieces of procedural code versus processing the entire load? In other words, if my workflow looks like this: Get work from queue0 and do A Store result from A in queue1 Get result from queue 1 and do B Store result from B in queue2 Get result from queue2 and do C Is there an inherent advantage to using 3 workers who each do the entire process themselves versus 3 workers that each do a part of the work (Worker 1 does 1 & 2, worker 2 does 3 & 4, worker 3 does 5). If we only care about working being done (finished with step 5) it would seem that it scales the same way (once you're using at least 3 workers). Maybe the big job is better because workers with that setup have less bottleneck issues?

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• Allow native DLL to output stdout / stderr in c# console application

  - by xaw

  I have a native DLL which outputs via stdout / stderr. I have a C# console application which calls this DLL and outputs binary data to a parent C# application which started the C# console exe, processing stdout / stderr. Currently when I call the C# exe it works just fine (the DLL hooks up to the stdout of my console application and puts its data in just fine). Is this by design (and shouldn't be broken in future .NET framework versions)? Are there limitations on my managed code's deployment with this strategy (full-trust, permission requirements, GAC issues, etc)? I can't seem to find any documentation about stdout with a managed exe and an unmanaged dll both putting data in that standard output on MSDN. Thanks,

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• SVN Mac oSX issue - permissions?

  - by Steve Griff

  Hello there, /Volumes/sites is a connection to a samba share that hosts some of our sites. We authorise using a username & password that is the same user/pass to log onto the mac. When committing, (or even doing a cleanup) from the Mac Client side using the svn command line tool or SCPlugin, this error occurs: Commit succeeded, but other errors follow: Error bumping revisions post-commit (details follow): In directory '/Volumes/sites/foobar/public_html' Error processing command 'committed' in '/Volumes/sites/foobar/public_html' Error replacing text-base of 'index.php' Can't move '/Volumes/sites/foobar/public_html/.svn/tmp/text-base/index.php.svn-base' to '/Volumes/sites/foobar/public_html/.svn/text-base/index.php.svn-base': Operation not permitted Any ideas? I think it's to do with permissions on the mac side not being able to move files around on the samba share. Apologies if my question is kinda vague so any extra information I can give please shout. Regards Steve

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• C# Application Becomes Slow and Unresponsive as String in Multiline Textbox Grows

  - by Jim Fell

  Hello. I have a C# application in which a LOT of information is being added to a Textbox for display to the user. Upon processing of the data, almost immediately, the application becomes very slow and unresponsive. This is how I am currently attempting to handle this: var saLines = textBox1.Lines; var saNewLines = saLines.Skip(50); textBox1.Lines = saNewLines.ToArray(); This code is run from a timer every 100mS. Is there a better way to handle this? I am using Microsoft Visual C# 2008 Express Edition. Thanks.

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• How Do I Convert text to a WAV file With Inaudible Waveform?

  - by Scott

  I am trying to create an audio watermarking system. I figure the best solution is to create an audio file (WAV) based on a unique string of text and then combine this with the original wav. The part that makes this tricky (for me anyway) is: How do I convert the text string to a wav? How do I ensure that the resulting WAV form is inaudible (or at least barely noticeable to the listener). I would prefer this be done server side (via PHP, etc) but if the processing load isn't too much then would be ok with something in Flash or Javascript. I'd be willing to pay someone to create me a workable solution (complete source code that functions as described). Thanks, Scott!

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• Graphics/Vision Interesting Topics

  - by Myx

  Hello: I would like to do an interesting project for a computer graphics course. I know that there is a lot of literature out there (i.e. SIGGRAPH conference papers). I have a very large range of interest with regard to computer graphics (i.e. image processing, 3D modeling, rendering, animation). However, I've only taken computer vision/graphics for 2 semesters and thus don't have too much background experience, except for the class projects that I had to do. I've been looking through SIGGRAPH papers trying to see if there is anything that will be of interest to me but the literature is extremely vast. I was wondering if anyone has any topic suggestions, anything interesting that you ran across that you could recommend. I would prefer to do something fun yet slightly challenging (not really interested in making a shooter game). If this question does not belong here, I apologize and please let me know where I should move it. Thanks!

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• Map Reduce Frameworks/Infrastructure

  - by Johannes Rudolph

  Map Reduce is a pattern that seems to get a lot of traction lately and I start to see it manifest in one of my projects that is focused on an event processing pipeline (iPhone Accelerometer and GPS data). I needed to built a lot of infrastructure for this project, in fact it overweighs the logic code interacting with it by 2x. Some of the components I built where EventProcessors (with in- and output plus buffering, timing etc.), multiplexers and aggregators. This leads me to my question what the "common" required infrastrucutre for map reduce is. Since I am working with .Net a lot I can see map reduce infrastructure built into the Framework and language constructs. Functional languages support this paradigm per se. It seems every language can be used with map reduce, some have better support than others, others again are built around that concept (e.g. Go). And there are Frameworks like Apache Hadoop to support map reduce.

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