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• Generating a canonical path

  - by Joel

  Does any one know of any Java libraries I could use to generate canonical paths (basically remove back-references). I need something that will do the following: Raw Path - Canonical Path /../foo/ -> /foo /foo/ -> /foo /../../../ -> / /./foo/./ -> /foo //foo//bar -> /foo/bar //foo/../bar -> /bar etc... At the moment I lazily rely on using: new File("/", path).getCanonicalPath(); But this resolves the path against the actual file system, and is synchronised. java.lang.Thread.State: BLOCKED (on object monitor) at java.io.ExpiringCache.get(ExpiringCache.java:55) - waiting to lock <0x93a0d180> (a java.io.ExpiringCache) at java.io.UnixFileSystem.canonicalize(UnixFileSystem.java:137) at java.io.File.getCanonicalPath(File.java:559) The paths that I am canonicalising do not exist on my file system, so just the logic of the method will do me fine, thus not requiring any synchronisation. I'm hoping for a well tested library rather than having to write my own.

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• Modify SQL result set before returning from stored procedure

  - by m0sa

  I have a simple table in my SQL Server 2008 DB: Tasks_Table -id -task_complete -task_active -column_1 -.. -column_N The table stores instructions for uncompleted tasks that have to be executed by a service. I want to be able to scale my system in future. Until now only 1 service on 1 computer read from the table. I have a stored procedure, that selects all uncompleted and inactive tasks. As the service begins to process tasks it updates the task_active flag in all the returned rows. To enable scaleing of the system I want to enable deployment of the service on more machines. Because I want to prevent a task being returned to more than 1 service I have to update the stored procedure that returns uncompleted and inactive tasks. I figured that i have to lock the table (only 1 reader at a time - I know I have to use an apropriate ISOLATION LEVEL), and updates the task_active flag in each row of the result set before returning the result set. So my question is how to modify the SELECT result set iin the stored procedure before returning it?

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• What can a company possibly gain by making Android phones hard to root?

  - by Chinmay Kanchi

  As someone who recently got a HTC Hero, I had to jump through several hoops to get root access on the phone to install custom firmware. Now, Android is open-source and fairly easy to build and hack on an emulator. It seems to be against the spirit of open-source to lock down a phone so you can't hack the phone itself. Now, often, there are understandable (though not always justifiable) reasons for locking a device down. For example, it might have proprietary software on it or you might want to retain control of the platform. However, Android by its open-source nature makes such concerns moot. Everyone and their dog has access to the userland code, and HTC is forced by the GPL to release kernel sources for each of their devices. So, I fail to see any motivation for alienating the hackers, when there is no possible benefit (in my mind) to be had from doing this. Any idea why a company would want to do this? Is it just short-sightedness or am I missing possible commercial implications of this?

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• For loop index out of range ArgumentOutOfRangeException when multithreading

  - by Lirik

  I'm getting some strange behavior... when I iterate over the dummyText List in the ThreadTest method I get an index out of range exception (ArgumentOutOfRangeException), but if I remove the threads and I just print out the text, then everything works fine. This is my main method: public static Object sync = new Object(); static void Main(string[] args) { ThreadTest(); Console.WriteLine("Press any key to continue."); Console.ReadKey(); } This method throws the exception: private static void ThreadTest() { Console.WriteLine("Running ThreadTest"); Console.WriteLine("Running ThreadTest"); List<String> dummyText = new List<string>() { "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten"}; for (int i = 0; i < dummyText.Count; i++) { Thread t = new Thread(() => PrintThreadName(dummyText[i])); // <-- Index out of range?!? t.Name = ("Thread " + (i)); t.IsBackground = true; t.Start(); } } private static void PrintThreadName(String text) { Random rand = new Random(DateTime.Now.Millisecond); while (true) { lock (sync) { Console.WriteLine(Thread.CurrentThread.Name + " running " + text); Thread.Sleep(1000+rand.Next(0,2000)); } } } This does not throw the exception: private static void ThreadTest() { Console.WriteLine("Running ThreadTest"); List<String> dummyText = new List<string>() { "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten"}; for (int i = 0; i < dummyText.Count; i++) { Console.WriteLine(dummyText[i]); // <-- No exception here } } Does anybody know why this is happening?

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• Access DB Transaction Insert limit

  - by user986363

  Is there a limit to the amount of inserts you can do within an Access transaction before you need to commit or before Access/Jet throws an error? I'm currently running the following code in hopes to determine what this maximum is. OleDbConnection cn = new OleDbConnection( @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\temp\myAccessFile.accdb;Persist Security Info=False;"); try { cn.Open(); oleCommand = new OleDbCommand("BEGIN TRANSACTION", cn); oleCommand.ExecuteNonQuery(); oleCommand.CommandText = "insert into [table1] (name) values ('1000000000001000000000000010000000000000')"; for (i = 0; i < 25000000; i++) { oleCommand.ExecuteNonQuery(); } oleCommand.CommandText = "COMMIT"; oleCommand.ExecuteNonQuery(); } catch (Exception ex) { } finally { try { oleCommand.CommandText = "COMMIT"; oleCommand.ExecuteNonQuery(); } catch{} if (cn.State != ConnectionState.Closed) { cn.Close(); } } The error I received on a production application when I reached 2,333,920 inserts in a single uncommited transaction was: "File sharing lock count exceeded. Increase MaxLocksPerFile registry entry". Disabling transactions fixed this problem.

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• Explanation of `self` usage during dealloc?

  - by Greg

  I'm trying to lock down my understanding of proper memory management within Objective-C. I've gotten into the habit of explicitly declaring self.myProperty rather than just myProperty because I was encountering occasional scenarios where a property would not be set to the reference that I intended. Now, I'm reading Apple documentation on releasing IBOutlets, and they say that all outlets should be set to nil during dealloc. So, I put this in place as follows and experienced crashes as a result: - (void)dealloc { [self.dataModel close]; [self.dataModel release], self.dataModel = nil; [super dealloc]; } So, I tried taking out the "self" references, like so: - (void)dealloc { [dataModel close]; [dataModel release], dataModel = nil; [super dealloc]; } This second system seems to work as expected. However, it has me a bit confused. Why would self cause a crash in that case, when I thought self was a fairly benign reference more used as a formality than anything else? Also, if self is not appropriate in this case, then I have to ask: when should you include self references, and when should you not?

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• How to modify Keyboard interrupt (under Windows XP) from a C++ Program ?

  - by rockr90

  Hi everyone ! We have been given a little project (As part of my OS course) to make a Windows program that modifies keyboard input, so that it transforms any lowercase character entered into an uppercase one (without using caps-lock) ! so when you type on the keyboard you'll see what you're typing transformed into uppercase ! I have done this quite easily using Turbo C by calling geninterrupt() and using variables _AH, _AL, i had to read a character using: _AH = 0x07; // Reading a character without echo geninterrupt(0x21); // Dos interrupt Then to transform it into an Upercase letter i have to mask the 5th bit by using: _AL = _AL & 0xDF; // Masking the entered character with 11011111 and then i will display the character using any output routine. Now, this solution will only work under old C DOS compilers. But what we intend to do is to make a close or similar solution to this by using any modern C/C++ compiler under Windows XP ! What i have first thought of is modifying the Keyboard ISR so that it masks the fifth bit of any entered character to turn it uppercase ! But i do not know how exactly to do this. Second, I wanted to create a Win32 console program to either do the same solution (but to no avail) or make a windows-compatible solution, still i do not know which functions to use ! Third I thought to make a windows program that modifies the ISR directly to suit my needs ! and i'm still looking for how to do this ! So please, If you could help me out on this, I would greatly appreciate it ! Thank you in advance ! (I'm using Windows XP on intel X86 with mingw-GCC compiler.)

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• Mysql for update

  - by shantanuo

  MySQL supports "for update" keyword. Here is how I tested that it is working as expected. I opened 2 browser tabs and executed the following commands in one window. mysql> start transaction; Query OK, 0 rows affected (0.00 sec) mysql> select * from myxml where id = 2 for update; .... mysql> update myxml set id = 3 where id = 2 limit 1; Query OK, 1 row affected, 1 warning (0.00 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> commit; Query OK, 0 rows affected (0.08 sec) In another window, I started the transaction and tried to take an update lock on the same record. mysql> start transaction; Query OK, 0 rows affected (0.00 sec) mysql> select * from myxml where id = 2 for update; Empty set (43.81 sec) As you can see from the above example, I could not select the record for 43 seconds as the transaction was being processed by another application in the Window No 1. Once the transaction was over, I got to select the record, but since the id 2 was changed to id 3 by the transaction that was executed first, no record was returned. My question is what are the disadvantages of using "for update" syntax? If I do not commit the transaction that is running in window 1 will the record be locked for-ever?

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• Preventing ActiveRecord save() on an instance

  - by Craig Walker

  I have an ActiveRecord model object Foo; it represents a standard database row. I want to be able to display modified versions of instances of this object. I'd like to reuse the class itself, as it already has all the hooks & aspects I'll need. (For example: I already have a view that displays the appropriate attributes). Basically I want to clone the model instance, modify some of its properties, and feed it back to the caller (view, test, etc). I do not want these attribute modifications getting back into the database. However, I do want to include the id attribute in the cloned version, as it makes dealing with the route-helpers much easier. Thus, I plan on calling ActiveRecord::Base.clone(), manually setting the ID of the cloned instance, and then making the appropriate attribute changes to the new instance. This has me worried though; one save() on the modified instance and my original data will get clobbered. So, I'm looking to lock down the new instance so that it won't hurt anything else. I'm already planning on calling freeze() (on the understanding that this prevents further modification to the object, though the documentation isn't terribly clear). However, I don't see any obvious way to prevent a save(). What would be the best approach to achieving this?

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• Rails problem with Delayed_Job and Active Record

  - by Michael Waxman

  I'm using Delayed_Job to grab a Twitter user's data from the API, but it's not saving it in the model for some reason! Please help! (code below) class BandJob < Struct.new(:band_id, :band_username) #parameter def perform require 'json' require 'open-uri' band = Band.find_by_id(band_id) t = JSON.parse(open("http://twitter.com/users/show/#{band_username}.json").read) band.screen_name = t['screen_name'] band.profile_background_image = t['profile_background_image_url'] band.url = 'http://' + band_username + '.com' band.save! end end To clarify, I'm actually not getting any errors, it's just not saving. Here's what my log looks like: * [JOB] acquiring lock on BandJob [4;36;1mDelayed::Job Update (3.1ms)[0m [0;1mUPDATE "delayed_jobs" SET locked_at = '2009-11-09 18:59:45', locked_by = 'host:dhcp128036151228.central.yale.edu pid:2864' WHERE (id = 10442 and (locked_at is null or locked_at < '2009-11-09 14:59:45') and (run_at <= '2009-11-09 18:59:45')) [0m [4;35;1mBand Load (1.5ms)[0m [0mSELECT * FROM "bands" WHERE ("bands"."id" = 34) LIMIT 1[0m [4;36;1mBand Update (0.6ms)[0m [0;1mUPDATE "bands" SET "updated_at" = '2009-11-09 18:59:45', "profile_background_image" = 'http://a3.twimg.com/profile_background_images/38193417/fbtile4.jpg', "url" = 'http://Coldplay.com', "screen_name" = 'coldplay' WHERE "id" = 34[0m [4;35;1mDelayed::Job Destroy (0.5ms)[0m [0mDELETE FROM "delayed_jobs" WHERE "id" = 10442[0m * [JOB] BandJob completed after 0.5448 1 jobs processed at 1.8011 j/s, 0 failed ... Thanks!

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• Parse large XML file w/ script or use BioPython API ?

  - by jeremy04

  Hey guys this is my first question on here. I'm trying to make a local copy of the UniprotKB in SQL. The UniprotKB is 2.1GB, and it comes in XML and a special text format used by SwissProt Here are my options: 1) Use a SAX parser (XML) - I chose Ruby, and Nokogiri. I started writing the parser, but my initial reaction: how would I map the XML schema to the SAX parser? 2) BioPython - I already have BioSQL/Biopython installed, which literally created my SQL schema for me, and I was able to successfully insert one SwissProt/Uniprot txt file into the database. I'm running it right now (crosses fingers) on the entire 2.1gb. Here is the code I'm running: from Bio import SeqIO from BioSQL import BioSeqDatabase from Bio import SwissProt server = BioSeqDatabase.open_database(driver = "MySQLdb", user = "root", passwd = "", host="localhost", db = "bioseqdb") db = server["uniprot"] iterator = SeqIO.parse(open("/path/to/uniprot_sprot.dat", "r"), "swiss") db.load(iterator) server.commit() Edit: it's now crashing because the transactions are getting locked (since the tables are Innodb) Error Number: 1205 Lock wait timeout exceeded; try restarting transaction. I'm using MySQL version: 5.1.43 Should I switch my database to Postgrelsql ?

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• Should I pass a SqlDataReader by reference or not when passing it out to multiple threads.

  - by deroby

  Hi all, being new to c# I've run into this 'conundrum' when passing around a SqlDataReader between different threads. Without going into too much detail, the idea is to have a main thread fetching data from the database (a large recordset) and then have a helper-task run through this record by record and doing some stuff based upon the contents of this. There is no feedback to the recordset, it simply wades through until no records are left. This works fine, but given the nature of the job at hand it should be possible to have this job spread over different threads (CPUs) to maximize throughput (the order of execution is of no significance). The question then becomes, when I pass this recordset in a SqlDataReader, do I have to use ref or not ? It kind of boils down to the question : if I pass the object around without specifying ref, won't it create new copies in memory and have records processed n times ? Or, don't I risk having the record-position being moved forward while not all fields have been fully read yet ? The latter seems more like a 'data racing' issue and probably is covered by the lock()ing mechanism (or not?). My initial take on the problem was that it doesn't really hurt passing the variable using ref, yet as a colleague put it : "you only need ref when you're doing something wrong" =) Additionally using ref restricts me from applying a Using() construction too which isn't very nice either. I thus create a "basic" project that tackles the same approach but without the ref notation. Tests so far show that it works flawlessly on a Core2Duo (2cpu) using any number of threads, yet I'm still a bit wary... What do you experts think about this ? Use ref or not ? You can find the test-project here as it seems I can't upload it to this question directly ?!? ps: it's just a test-project and I'm new to c#, so please be gentle on me when breaking down the code =P

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• Passing variables from a thread to another form using C#

  - by kirstom14

  Hi, I am trying to pass 2 variables from a thread, in the MainForm, to another form, but when doing so an error occurs. private void TrackingThread( ) { float targetX = 0; float targetY = 0; while ( true ) { camera1Acquired.WaitOne( ); camera2Acquired.WaitOne( ); lock ( this ) { // stop the thread if it was signaled if ( ( x1 == -1 ) && ( y1 == -1 ) && ( x2 == -1 ) && ( y2 == -1 ) ) { break; } // get middle point targetX = ( x1 + x2 ) / 2; targetY = ( y1 + y2 ) / 2; } if (directionForm != null) { directionForm.RunMotors(targetX, targetY); } } } In the form, directionForm, I am simply displaying the variables targetX and targetY. The code for the directionForm.RunMotors() is the following: public void RunMotors(float x, float y) { label1.Text = "X-ordinate " + x.ToString(); label2.Text = "Y-ordinate " + y.ToString(); } The error happen when I am trying to display the two variables: "InvalidOperationException was unhandled Cross-threading operation not valid: Control label1 accessed from a thread other than . the thread it was created on" What shall I do??? Thanks in advance

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• Anyone NOT using a Web Framework? Why?

  - by tom

  I'm well aware of the many reasons to use a web framework. I'm just wondering whether anyone out there is using absolutely no web framework whatsoever to develop their web projects. I would really love to know the reason(s) why you're not using a web framework. For the sake of this discussion, your programming language of choice does not matter. Some possibilities for discussion: You don't hide behind an ORM. You don't rely on any sort of templating system. You think MVC is a really nice TLA but lacks an essential vowel or two. No need for any additional javascript framework tomfoolery. You just write as much code as possible in your native programming language(s). Summary of reasons thus far: Language learning opportunities. Specific performance reasons (write-intensive transaction processing). Seeking more nuanced control over your data and applications (less abstraction). You're building your own framework! Prove to yourself that you can succeed (or fail) just like the big framework-building gurus. Integration issues with unpopular/legacy technologies (exotic databases or protocols come to mind). Big company, lots of code, no talent nor buy-in present to move to a web framework. Some frameworks really lock you in and cannot perpetually grow along with your needs. These few black sheep don't make it easy to jump outside of the framework, write some custom code, and easily jump back in. When you finally escape the asylum, you'll never look back.

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• EventAggregator, is it thread-safe?

  - by pfaz

  Is this thread-safe? The EventAggregator in Prism is a very simple class with only one method. I was surprised when I noticed that there was no lock around the null check and creation of a new type to add to the private _events collection. If two threads called GetEvent simultaneously for the same type (before it exists in _events) it looks like this would result in two entries in the collection. /// <summary> /// Gets the single instance of the event managed by this EventAggregator. Multiple calls to this method with the same <typeparamref name="TEventType"/> returns the same event instance. /// </summary> /// <typeparam name="TEventType">The type of event to get. This must inherit from <see cref="EventBase"/>.</typeparam> /// <returns>A singleton instance of an event object of type <typeparamref name="TEventType"/>.</returns> public TEventType GetEvent<TEventType>() where TEventType : EventBase { TEventType eventInstance = _events.FirstOrDefault(evt => evt.GetType() == typeof(TEventType)) as TEventType; if (eventInstance == null) { eventInstance = Activator.CreateInstance<TEventType>(); _events.Add(eventInstance); } return eventInstance; }

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• Is there any point in using a volatile long?

  - by Adamski

  I occasionally use a volatile instance variable in cases where I have two threads reading from / writing to it and don't want the overhead (or potential deadlock risk) of taking out a lock; for example a timer thread periodically updating an int ID that is exposed as a getter on some class: public class MyClass { private volatile int id; public MyClass() { ScheduledExecutorService execService = Executors.newScheduledThreadPool(1); execService.scheduleAtFixedRate(new Runnable() { public void run() { ++id; } }, 0L, 30L, TimeUnit.SECONDS); } public int getId() { return id; } } My question: Given that the JLS only guarantees that 32-bit reads will be atomic is there any point in ever using a volatile long? (i.e. 64-bit). Caveat: Please do not reply saying that using volatile over synchronized is a case of pre-optimisation; I am well aware of how / when to use synchronized but there are cases where volatile is preferable. For example, when defining a Spring bean for use in a single-threaded application I tend to favour volatile instance variables, as there is no guarantee that the Spring context will initialise each bean's properties in the main thread.

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• Boost::Thread linking error on OSX?

  - by gct

  So I'm going nuts trying to figure this one out. Here's my basic setup: I'm compiling a shared library with a bunch of core functionality that uses a lot of boost stuff. We'll call this library libpf_core.so. It's linked with the boost static libraries, specifically the python, system, filesystem, thread, and program_options libraries. This all goes swimmingly. Now, I have a little test program called test_socketio which is compiled into a shared library (it's loaded as a plugin at runtime). It uses some boost stuff like boost::bind and boost::thread, and it's linked again libpf_core.so (which has the boost libraries included remember). When I go to compile test_socketio though, out of all my plugins it gives me a linking error: [ Building test_socketio ] g++ -c -pg -g -O0 -I/usr/local/include -I../include test_socketio.cc -o test_socketio.o g++ -shared test_socketio.o -lpy_core -o test_socketio.so Undefined symbols: "boost::lock_error::lock_error()", referenced from: boost::unique_lock<boost::mutex>::lock() in test_socketio.o ld: symbol(s) not found collect2: ld returned 1 exit status And I'm going crazy trying to figure out why this is. I've tried explicitly linking boost::thread into the plugin to no avail, tried ensuring that I'm using the boost headers associated with the libraries linked into libpf_core.so in case there was a conflict there. Is there something OSX specific regarding boost that I'm missing? In my searching on google I've seen a number of other people get this error but no one seems to have come up with a satisfactory solution.

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• Thread synchronization and aborting.

  - by kubal5003

  Hello, I've got a little problem with ending the work of one of my threads. First things first so here's the app "layout": Thread 1 - worker thread (C++/CLI) - runs and terminates as expected for(...) { try { if(TabuStop) return; System::Threading::Monitor::Enter("Lock1"); //some work, unmanaged code } finally { if(stop) { System::Threading::Monitor::Pulse("Lock1"); } else { System::Threading::Monitor::Pulse("Lock1"); System::Threading::Monitor::Wait("Lock1"); } } } Thread 2 - display results thread (C#) while (WorkerThread.IsAlive) { lock ("Lock1") { if (TabuEngine.TabuStop) { Monitor.Pulse("Lock1"); } else { Dispatcher.BeginInvoke(RefreshAction); Monitor.Pulse("Lock1"); Monitor.Wait("Lock1", 5000); } } // Thread.Sleep(5000); } I'm trying to shut the whole thing down from app main thread like this: TabuEngine.TabuStop = true; //terminates nicely the worker thread and if (DisplayThread.IsAlive) { DisplayThread.Abort(); } I also tried using DisplayThread.Interrupt, but it always blocks on Monitor.Wait("Lock1", 5000); and I can't get rid of it. What is wrong here? How am I supposed to perform the synchronization and let it do the work that it is supposed to do? //edit I'm not even sure now if the trick with using "Lock1" string is really working and locks are placed on the same object..

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• AFNetworking iOS

  - by Jeromiin

  I have a problem with a request in my app, I want to receive a json but because of the completion block my "PRINT 2" is print before my "PRINT 1" and of course my "PRINT 2" is null. I want the contrary and my "PRINT 2" to be filled but I can't manage to do it. -(void) makeConnection { NSURL *url = [NSURL URLWithString:[@"http://monsite.com/iPhonej/verifPseudo.php?login="stringByAppendingString:[_loginField.text stringByAppendingString:[@"&password=" stringByAppendingString:_passField.text]]]]; NSURLRequest *request = [NSURLRequest requestWithURL:url]; AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request]; operation.responseSerializer = [AFJSONResponseSerializer serializer]; [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) { self.response = (NSDictionary *)responseObject; NSLog(@"PRINT 1 : %@", self.response[@"la"][@"reponse"][0][@"rep"]); [_dataLock lock]; } failure:^(AFHTTPRequestOperation *operation, NSError *error) { NSLog(@"Request Failed: %@, %@", error, error.userInfo); }]; [operation start]; } - (IBAction)logIn:(id)sender { [self makeConnection]; NSLog(@"PRINT 2 : %@", self.response[@"la"][@"reponse"][0][@"rep"]); } I know that AFNetworking is asynchronous but is there an other way to do the request and receive my json well ? Thank you

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• Multithreaded linked list traversal

  - by Rob Bryce

  Given a (doubly) linked list of objects (C++), I have an operation that I would like multithread, to perform on each object. The cost of the operation is not uniform for each object. The linked list is the preferred storage for this set of objects for a variety of reasons. The 1st element in each object is the pointer to the next object; the 2nd element is the previous object in the list. I have solved the problem by building an array of nodes, and applying OpenMP. This gave decent performance. I then switched to my own threading routines (based off Windows primitives) and by using InterlockedIncrement() (acting on the index into the array), I can achieve higher overall CPU utilization and faster through-put. Essentially, the threads work by "leap-frog'ing" along the elements. My next approach to optimization is to try to eliminate creating/reusing the array of elements in my linked list. However, I'd like to continue with this "leap-frog" approach and somehow use some nonexistent routine that could be called "InterlockedCompareDereference" - to atomically compare against NULL (end of list) and conditionally dereference & store, returning the dereferenced value. I don't think InterlockedCompareExchangePointer() will work since I cannot atomically dereference the pointer and call this Interlocked() method. I've done some reading and others are suggesting critical sections or spin-locks. Critical sections seem heavy-weight here. I'm tempted to try spin-locks but I thought I'd first pose the question here and ask what other people are doing. I'm not convinced that the InterlockedCompareExchangePointer() method itself could be used like a spin-lock. Then one also has to consider acquire/release/fence semantics... Ideas? Thanks!

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• Callers block until getFoo() has a value ready?

  - by Sean Owen

  I have a Java Thread which exposes a property which other threads want to access: class MyThread extends Thread { private Foo foo; ... Foo getFoo() { return foo; } ... public void run() { ... foo = makeTheFoo(); ... } } The problem is that it takes some short time from the time this runs until foo is available. Callers may call getFoo() before this and get a null. I'd rather they simply block, wait, and get the value once initialization has occurred. (foo is never changed afterwards.) It will be a matter of milliseconds until it's ready, so I'm comfortable with this approach. Now, I can make this happen with wait() and notifyAll() and there's a 95% chance I'll do it right. But I'm wondering how you all would do it; is there a primitive in java.util.concurrent that would do this, that I've missed? Or, how would you structure it? Yes, make foo volatile. Yes, synchronize on an internal lock Object and put the check in a while loop until it's not null. Am I missing anything?

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• What are salesforce.com and Apex like as an application development platform?

  - by mhollers

  I have recently discovered that salesforce.com is much more than an online CRM after coming across a Morrison's Case Study in which they develop a works management application. I've been trying it out with a view to recreating our own Works Management system on the platform. My background is in Microsoft and .Net, and the obvious 1st choice would be asp.net. However, there's only really myself with .net experience and my manager with a more legacy Synergy programming background, and I am self taught and am looking at evaluating other RAD options (eg Ironspeed). the nature of the business is in the main 2-5 concurrent construction type contracts that run for 3-5 yrs each, each requiring 15-50 system users. Traditionally we have used our character based Works Mangement system for everything and tweaked it for each contract. The Salesforce licensing model on the face of it suits this sort of flexibilty, but I'm worried about the development flexibilty/learning curve and all the issues that surround lock-in. There doesn't seem to be much neutral sober analysis of the platform on the web that isn't salesforce's own material/blogs Has anyone any experience of developing an application on salesforce as compared to the more 'traditional' .Net route?

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• I have a fucntion that create histogram of each Bitmap. How can i create another 3 histograms for R.G.B of each Bitmap?

  - by Daniel Lip

  This is the histogram function im using today and if im not worng it's creating an histogram by Gray color. What i want is another fucntion that will return me 3 histograms of each Bitmap: The first histogram will be of the Red color of the bitmap the second for the Green color and the last one for the Blue color. public static long[] GetHistogram(Bitmap b) { long[] myHistogram = new long[256]; BitmapData bmData = null; try { //Lock it fixed with 32bpp bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb); int scanline = bmData.Stride; System.IntPtr Scan0 = bmData.Scan0; unsafe { byte* p = (byte*)(void*)Scan0; int nWidth = b.Width; int nHeight = b.Height; for (int y = 0; y < nHeight; y++) { for (int x = 0; x < nWidth; x++) { long Temp = 0; Temp += p[0]; // p[0] - blue, p[1] - green , p[2]-red Temp += p[1]; Temp += p[2]; Temp = (int)Temp / 3; myHistogram[Temp]++; //we do not need to use any offset, we always can increment by pixelsize when //locking in 32bppArgb - mode p += 4; } } } b.UnlockBits(bmData); } catch { try { b.UnlockBits(bmData); } catch { } } return myHistogram; } How may i do it ?

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• Mercurial Subrepos, how to control which changeset I want to use for a subrepo?

  - by Lasse V. Karlsen

  I am reading up on subrepos, and have been running some tests locally, seems to work OK so far, but I have one question. How do I specify/control which changeset I want to use for a particular subrepo? For instance, let's say I have the following two projects: class library application o fourth commit o second commit, added a feature | | o third commit o initial commit | | o second commit |/ o initial commit Now, I want the class library as a subrepo of my application, but due to the immaturity of the longest branch (the one ending up as fourth commit), I want to temporarily use the "second commit" tip. How do I go about configuring that, assuming it is even possible? Here's a batch file that sets up the above two repos + adds the library as a subrepo. If you run the batch file, it will output: [C:\Temp] :test ... v4 As you can see from that last line there, it verifies the contents of the file in the class library, which is "v4" from the fourth commit. I'd like it to be "v2", and persist as "v2" until I'm ready to pull down a newer version from the class library repository. Can anyone tell me if it is possible to do what I want, and if so, what I need to do in order to lock my subrepo to the right changeset? Batch-file: @echo off if exist app rd /s /q app if exist lib rd /s /q lib if exist app-clone rd /s /q app-clone rem == app == hg init app cd app echo program>main.txt hg add main.txt hg commit -m "initial commit" echo program+feature1>main.txt hg commit -m "second commit, added a feature" cd .. rem == lib == hg init lib cd lib echo v1>lib.txt hg add lib.txt hg commit -m "initial commit" echo v2>lib.txt hg commit -m "second commit" hg update 0 echo v3>lib.txt hg commit -m "third commit" echo v4>lib.txt hg commit -m "fourth commit" cd .. rem == subrepos == cd app hg clone ..\lib lib echo lib = ..\lib >.hgsub hg add .hgsub hg commit -m "added subrepo" cd .. rem == clone == hg clone app app-clone type app-clone\lib\lib.txt

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• Parameter meaning of CBasePin::GetMediaType(int iPosition, ...) method

  - by user325320

  Thanks to everyone who views my question. http://msdn.microsoft.com/en-us/library/windows/desktop/dd368709(v=vs.85).aspx It is not very clear from the documentation regarding the iPosition parameter for virtual HRESULT GetMediaType( int iPosition, CMediaType *pMediaType ); It is said "Zero-based index value.", but what kind of index it is? the index of the samples? I have a source filter sending the H.264 NALU flows (MEDIASUBTYPE_AVC1) and it works very well except that the SPS/PPS may be changed after the video is played for a while. The SPS and PPS are appended to the MPEG2VIDEOINFO structure, which is passed in CMediaType::SetFormat method when GetMediaType method is called. and there is another version of GetMediaType which accepts the iPosition parameter. It seems I can use this method to update the SPS / PPS. My question is: What does the iPosition param mean, and how does Decoder Filter know which SPS/PPS are assigned for each NALU sample. HRESULT GetMediaType(int iPosition, CMediaType *pMediaType) { ATLTRACE( "\nGetMediaType( iPosition = %d ) ", iPosition); CheckPointer(pMediaType,E_POINTER); CAutoLock lock(m_pFilter->pStateLock()); if (iPosition < 0) { return E_INVALIDARG; } if (iPosition == 0) { pMediaType->InitMediaType(); pMediaType->SetType(&MEDIATYPE_Video); pMediaType->SetFormatType(&FORMAT_MPEG2Video); pMediaType->SetSubtype(&MEDIASUBTYPE_AVC1); pMediaType->SetVariableSize(); } int nCurrentSampleID; DWORD dwSize = m_pFlvFile->GetVideoFormatBufferSize(nCurrentSampleID); LPBYTE pBuffer = pMediaType->ReallocFormatBuffer(dwSize); memcpy( pBuffer, m_pFlvFile->GetVideoFormatBuffer(nCurrentSampleID), dwSize); pMediaType->SetFormat(pBuffer, dwSize); return S_OK; }

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