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• [Java] Cluster Shared Cache

  - by GuiSim

  Hi everyone. I am searching for a java framework that would allow me to share a cache between multiple JVMs. What I would need is something like Hazelcast but without the "distributed" part. I want to be able to add an item in the cache and have it automatically synced to the other "group member" cache. If possible, I'd like the cache to be sync'd via a reliable multicast (or something similar). I've looked at Shoal but sadly the "Distributed State Cache" seems like an insufficient implementation for my needs. I've looked at JBoss Cache but it seems a little overkill for what I need to do. I've looked at JGroups, which seems to be the most promising tool for what I need to do. Does anyone have experiences with JGroups ? Preferably if it was used as a shared cache ? Any other suggestions ? Thanks ! EDIT : We're starting tests to help us decide between Hazelcast and Infinispan, I'll accept an answer soon. EDIT : Due to a sudden requirements changes, we don't need a distributed map anymore. We'll be using JGroups for a low level signaling framework. Thanks everyone for you help.

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• Why does the following Toggle function perform four different operations instead of two?

  - by marcamillion

  You can see the implementation here: http://jsfiddle.net/BMWZd/8/ What I am trying to do, when you click on 'John Brown', you see the first element at top turn black. When you click it again, the border of the dotted circle disappears, then when you click 'John Brown' again, you see something else, then finally once again it all disappears. What I am trying to achieve is when you click it once, everything turns black (like it does now), then you click it again, everything disappears and goes back to the original state. Important distinction, what I mean is...when one of the names in the box are not clicked. So if you clicked John Brown then moved to Jack Dorsey, the #1 at top should stay black. But if you were to click Jack Dorsey again, i.e. you 'unclicked' it, then it should disappear. Also, how do I tighten it up, so that it responds quicker. Now when you click it, it feels like there is a little bit of a lag between when it was clicked and when it responds. Edit1: If anyone is interested...the UI that this will be used in is for my webapp - http://www.compversions.com

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• Multiple threads modifying a collection in Java??

  - by posdef

  Hi, The project I am working on requires a whole bunch of queries towards a database. In principle there are two types of queries I am using: read from excel file, check for a couple of parameters and do a query for hits in the database. These hits are then registered as a series of custom classes. Any hit may (and most likely will) occur more than once so this part of the code checks and updates the occurrence in a custom list implementation that extends ArrayList. for each hit found, do a detail query and parse the output, so that the classes created in (I) get detailed info. I figured I would use multiple threads to optimize time-wise. However I can't really come up with a good way to solve the problem that occurs with the collection these items are stored in. To elaborate a little bit; throughout the execution objects are supposed to be modified by both (I) and (II). I deliberately didn't c/p any code, as it would be big chunks of code to make any sense.. I hope it make some sense with the description above. Thanks,

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• Reading same file from multiple threads in C#

  - by Gustavo Rubio

  Hi. I was googling for some advise about this and I found some links. The most obvious was this one but in the end what im wondering is how well my code is implemented. I have basically two classes. One is the Converter and the other is ConverterThread I create an instance of this Converter class that has a property ThreadNumber that tells me how many threads should be run at the same time (this is read from user) since this application will be used on multi-cpu systems (physically, like 8 cpu) so it is suppossed that this will speed up the import The Converter instance reads a file that can range from 100mb to 800mb and each line of this file is a tab-delimitted value record that is imported to another destination like a database. The ConverterThread class simply runs inside the thread (new Thread(ConverterThread.StartThread)) and has event notification so when its work is done it can notify the Converter class and then I can sum up the progress for all these threads and notify the user (in the GUI for example) about how many of these records have been imported and how many bytes have been read. It seems, however that I'm having some trouble because I get random errors about the file not being able to be read or that the sum of the progress (percentage) went above 100% which is not possible and I think that happens because threads are not being well managed and probably the information returned by the event is malformed (since it "travels" from one thread to another) Do you have any advise on better practices of implementation of threads so I can accomplish this? Thanks in advance.

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• casting Collection<SomeClass> to Collection<SomeSuperClass>

  - by skrebbel

  Hi all, I'm sure this has been answered before, but I really cannot find it. I have a java class SomeClass and an abstract class SomeSuperClass. SomeClass extends SomeSuperClass. Another abstract method has a method that returns a Collection<SomeSuperClass>. In an implementation class, I have a Collection<SomeClass> myCollection I understand that I cannot just return myCollection, because Collection<SomeClass> does not inherit from Collection<SomeSuperClass>. Nevertheless, I know that everything in myCollection is a SomeSuperClass because after all, they're SomeClass objects which extend SomeSuperClass. How can I make this work? I.e. I want public class A { private Collection<SomeClass> myCollection; public Collection<SomeSuperClass> getCollection() { return myCollection; //compile error! } } The only way I've found is casting via a non-generic type and getting unchecked warnings and whatnot. There must be a more elegant way, though? I feel that also using Collections.checkedSet() and friends are not needed, since it is statically certain that the returned collection only contains SomeClass objects (this would not be the case when downcasting instead of upcasting, but that's not what I'm doing). What am I missing? Thanks!

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• Strange constructor

  - by Bilthon

  Well, I'm gonna be pretty straightforward here, I just have a piece of code in c++ which I'm not sure I really understand and need some help with. Ok, to simplify lets just say I have a class that is defined like this: (the real class is a little bit more complicated, but this is what matters) class myClass : public Runnable { Semaphore *m_pMySemaphore; __Queue<Requests> *m_pQueue; Request m_Request; VetorSlotBuffer *m_vetorSlotBuffer; } Up to here nothing is wrong, myClass is just a regular class which has 3 members that actually are pointers to other classes and an object of the class Request, the implementation of those classes not being important for my point here. Then when this person implemented the constructor for myClass he or she did this: myClass::myClass() : m_pMySemaphore(0), m_pQueue(0), m_vetorSlotBuffer(0) { } It's pretty evident that those three variables are treated like that by the constructor because they are pointers, am I right? but what kind of syntax is that? am I setting the pointers to null by doing that? I've seen a little bit of c++ already but never found something like that. And secondly, what's the deal with the ":" after the constructor declaration? that I've seen but never took the time to investigate. Is this like an inner class or something? Thank you very much in advance. Nelson R. Perez

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• iPhone: Creating a hierarchy-based table navigation.

  - by Jack Griffiths

  Hi there, I've tried to ask this before, but nothing got answered. Basically, I would like someone to explain to me how to create a table, which when a cell is tapped, pushes the user to the next view for that cell. I have this so far: Click here to view what I have. I would further like to, say when CSS is tapped, it goes to a new view which has another table in it. This table would then take the user to a detail view, which is scrollable and you can switch pages through it. I would appreciate longer, more structured tutorials on how to do each and every bit to get it to work. Here's my array in my implementation file: - (void)viewDidLoad { arryClientSide = [[NSArray alloc] initWithObjects:@"CSS", @"HTML", @"JavaScript", @"XML", nil]; arryServerSide = [[NSArray alloc] initWithObjects:@"Apache", @"PHP", @"SQL", nil]; self.title = @"Select a Language"; [super viewDidLoad]; } and my .h: @interface RootViewController : UITableViewController <UITableViewDelegate, UITableViewDataSource> { IBOutlet UITableView *tblSimpleTable; NSArray *arryClientSide; NSArray *arryServerSide; } My current code crashes the script, and this error is returned in the console: Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[UITableViewController loadView] loaded the "NextView" nib but didn't get a UITableView.' If that error is the source of why it's not pushing, then an explanation of how to remedy that would also be appreciated Many thanks, Jack

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• Drupal 6 node_view empty

  - by kristian nissen

  I'm trying to produce a page with a list of specific nodes but the node_view returns an empty string. This is my query: function events_upcoming() { $output = ''; $has_events = false; $res = pager_query(db_rewrite_sql("SELECT n.nid, n.created FROM {node} n WHERE n.type = 'events' AND n.status = 1 ORDER BY n.sticky DESC, n.created DESC"), variable_get('default_nodes_main', 10)); while ($n = db_fetch_object($res)) { $output .= node_view(node_load($n->nid), 1); $has_events = true; } if ($has_events) { $output .= theme('pager', NULL, variable_get('default_nodes_main', 10)); } return $output; } hook_menu (part of): 'events/upcoming' => array( 'title' => t('Upcoming Events'), 'page callback' => 'events_upcoming', 'access arguments' => array('access content'), 'type' => MENU_SUGGESTED_ITEM ), the implementation of hook_view: function events_view($node, $teaser = false, $page = false) { $node = node_prepare($node, $teaser); if ($page) { // TODO: Handle breadcrump } return $node; } now, if I add a var_dump($node) inside events_view the node is present and I can see the values I want, and if I add a var_dump inside while loop in events_upcoming I also get a node id from the query. the strange thing is, when I load localhost/events/upcoming I see the pager and nothing else. I have used the blog.module as a reference, but what am I missing here?

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• Why is there no autorelease pool when I do performSelectorInBackground: ?

  - by Thanks

  I am calling a method that goes in a background thread: [self performSelectorInBackground:@selector(loadViewControllerWithIndex:) withObject:[NSNumber numberWithInt:viewControllerIndex]]; then, I have this method implementation that gets called by the selector: - (void) loadViewControllerWithIndex:(NSNumber *)indexNumberObj { NSAutoreleasePool *arPool = [[NSAutoreleasePool alloc] init]; NSInteger vcIndex = [indexNumberObj intValue]; Class c; UIViewController *controller = [viewControllers objectAtIndex:vcIndex]; switch (vcIndex) { case 0: c = [MyFirstViewController class]; break; case 1: c = [MySecondViewController class]; break; default: NSLog(@"unknown index for loading view controller: %d", vcIndex); // error break; } if ((NSNull *)controller == [NSNull null]) { controller = [[c alloc] initWithNib]; [viewControllers replaceObjectAtIndex:vcIndex withObject:controller]; [controller release]; } if (controller.view.superview == nil) { UIView *placeholderView = [viewControllerPlaceholderViews objectAtIndex:vcIndex]; [placeholderView addSubview:controller.view]; } [arPool release]; } Althoug I do create an autorelease pool there for that thread, I always get this error: 2009-05-30 12:03:09.910 Demo[1827:3f03] *** _NSAutoreleaseNoPool(): Object 0x523e50 of class NSCFNumber autoreleased with no pool in place - just leaking Stack: (0x95c83f0f 0x95b90442 0x28d3 0x2d42 0x95b96e0d 0x95b969b4 0x93a00155 0x93a00012) If I take away the autorelease pool, I get a whole bunch of messages like these. I also tried to create an autorelease pool around the call of the performSelectorInBackground:, but that doesn't help. I suspect the parameter, but I don't know why the compiler complains about an NSCFNumber. Am I missing something? My Instance variables are all "nonatomic". Can that be a problem? UPDATE: I may also suspect that some variable has been added to an autorelease pool of the main thread (maybe an ivar), and now it trys to release that one inside the wrong autorelease pool? If so, how could I fix that? (damn, this threading stuff is complex ;) )

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• Is there a better way of making numpy.argmin() ignore NaN values

  - by Dragan Chupacabrovic

  Hello Everybody, I want to get the index of the min value of a numpy array that contains NaNs and I want them ignored >>> a = array([ nan, 2.5, 3., nan, 4., 5.]) >>> a array([ NaN, 2.5, 3. , NaN, 4. , 5. ]) if I run argmin, it returns the index of the first NaN >>> a.argmin() 0 I substitute NaNs with Infs and then run argmin >>> a[isnan(a)] = Inf >>> a array([ Inf, 2.5, 3. , Inf, 4. , 5. ]) >>> a.argmin() 1 My dilemma is the following: I'd rather not change NaNs to Infs and then back after I'm done with argmin (since NaNs have a meaning later on in the code). Is there a better way to do this? There is also a question of what should the result be if all of the original values of a are NaN? In my implementation the answer is 0

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• Sending series of images to display like a movie on iPhone

  - by unknownthreat

  Allow me to elaborate more. On the server, we will have a program that will take data from iPhone and process that data and produce series of images. Each time an image is generated, it will be send back to display on iPhone. I have done all of the things above using UDP, OpenGL, and such. It works. The images are transferred to iPhone and can be displayed, but it is slow. The image's resolution is around 320 x 420 and we send the image pixels by pixels. This naive implementation leads to a slow framerate. I can see around 2-3 frames per second. There are also some UDP packets dropped, and this is expected. Are there any sort of compression method available for something like this? Are there any other method that can make this better? NOTE: please don't just write "compression" as an answer, because we are aware that we will need to do it in some ways.

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• Is there a fast alternative to creating a Texture2D from a Bitmap object in XNA?

  - by Matthew Bowen

  I've looked around a lot and the only methods I've found for creating a Texture2D from a Bitmap are: using (MemoryStream s = new MemoryStream()) { bmp.Save(s, System.Drawing.Imaging.ImageFormat.Png); s.Seek(0, SeekOrigin.Begin); Texture2D tx = Texture2D.FromFile(device, s); } and Texture2D tx = new Texture2D(device, bmp.Width, bmp.Height, 0, TextureUsage.None, SurfaceFormat.Color); tx.SetData<byte>(rgbValues, 0, rgbValues.Length, SetDataOptions.NoOverwrite); Where rgbValues is a byte array containing the bitmap's pixel data in 32-bit ARGB format. My question is, are there any faster approaches that I can try? I am writing a map editor which has to read in custom-format images (map tiles) and convert them into Texture2D textures to display. The previous version of the editor, which was a C++ implementation, converted the images first into bitmaps and then into textures to be drawn using DirectX. I have attempted the same approach here, however both of the above approaches are significantly too slow. To load into memory all of the textures required for a map takes for the first approach ~250 seconds and for the second approach ~110 seconds on a reasonable spec computer. If there is a method to edit the data of a texture directly (such as with the Bitmap class's LockBits method) then I would be able to convert the custom-format images straight into a Texture2D and hopefully save processing time. Any help would be very much appreciated. Thanks

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• FTP FileWatcher

  - by Meiscooldude

  So, I am in this little predicament where I am stuck watching a few ftp folders to see if they have new files added to them. If they do, it needs to throw an event with the file name. Thereby telling something else to download that file. This is a pretty simple object to make, I was just curious if anyone knew how expensive this operation would be? I plan on using the command NLIST because I don't need file size information, and there will be no sub-directories in the folder. Each file in the folder will have exactly 25 characters in its name. There could be anywhere from 10 to 'maybe' a couple thousand (max around 2000) files per folder (usually on the lower end, 100-300, but currently growing). The files are anywhere from 250kb to a very VERY unlikely 10mb (usually within the 250kb to 4mb range). There possibly could be up to a few hundred folders (in which case I could change the watch frequency depending on number of folders), but currently there are only a few (6-10ish). There also would be multiple logins for the ftp server, different logins would have access to different folders. I am not asking for an implementation, just if anyone has some first or second hand knowledge about FTP, how could this affect my network. I am not opposed to putting in file retention times or change the frequency in which I check for new files.

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• Demangling typeclass functions in GHC profiler output

  - by Paul Kuliniewicz

  When profiling a Haskell program written in GHC, the names of typeclass functions are mangled in the .prof file to distinguish one instance's implementations of them from another. How can I demangle these names to find out which type's instance it is? For example, suppose I have the following program, where types Fast and Slow both implement Show: import Data.List (foldl') sum' = foldl' (+) 0 data Fast = Fast instance Show Fast where show _ = show $ sum' [1 .. 10] data Slow = Slow instance Show Slow where show _ = show $ sum' [1 .. 100000000] main = putStrLn (show Fast ++ show Slow) I compile with -prof -auto-all -caf-all and run with +RTS -p. In the .prof file that gets generated, I see that the top cost centers are: COST CENTRE MODULE %time %alloc show_an9 Main 71.0 83.3 sum' Main 29.0 16.7 And in the tree, I likewise see (omitting irrelevant lines): individual inherited COST CENTRE MODULE no. entries %time %alloc %time %alloc main Main 232 1 0.0 0.0 100.0 100.0 show_an9 Main 235 1 71.0 83.3 100.0 100.0 sum' Main 236 0 29.0 16.7 29.0 16.7 show_anx Main 233 1 0.0 0.0 0.0 0.0 How do I figure out that show_an9 is Slow's implementation of show and not Fast's?

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• Delphi Unicode String Type Stored Directly at its Address (or "Unicode ShortString")

  - by Andreas Rejbrand

  I want a string type that is Unicode and that stores the string directly at the adress of the variable, as is the case of the (Ansi-only) ShortString type. I mean, if I declare a S: ShortString and let S := 'My String', then, at @S, I will find the length of the string (as one byte, so the string cannot contain more than 255 characters) followed by the ANSI-encoded string itself. What I would like is a Unicode variant of this. That is, I want a string type such that, at @S, I will find a unsigned 32-bit integer (or a single byte would be enough, actually) containing the length of the string in bytes (or in characters, which is half the number of bytes) followed by the Unicode representation of the string. I have tried WideString, UnicodeString, and RawByteString, but they all appear only to store an adress at @S, and the actual string somewhere else (I guess this has do do with reference counting and such). Update: The most important reason for this is probably that it would be very problematic if sizeof(string) were variable. I suspect that there is no built-in type to use, and that I have to come up with my own way of storing text the way I want (which actually is fun). Am I right? Update I will, among other things, need to use these strings in packed records. I also need manually to read/write these strings to files/the heap. I could live with fixed-size strings, such as <= 128 characters, and I could redesign the problem so it will work with null-terminated strings. But PChar will not work, for sizeof(PChar) = 1 - it's merely an address. The approach I eventually settled for was to use a static array of bytes. I will post my implementation as a solution later today.

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• How to build a sequence in the method calls of a fluent interface

  - by silverfighter

  Hi I would like to build a fluent interface for creating am object some sort of factory or builder. I understand that I have to "return this" in order to make the methods chainable. public class CarBuilder { public CarBuilder() { car = new Car(); } private Car car; public CarBuilder AddEngine(IEngineBuilder engine) { car.Engine = engine.Engine(); return this; } public CarBuilder AddWheels(IWheelsBuilder wheels) { car.Wheels = wheels.Wheels(); return this; } public CarBuilder AddFrame(IFrameBuilder frame) { car.Frame = frame.Frame(); return this; } public Car BuildCar() { return car; } } with this I could build a car like that: Car c = builder.AddFrame(fBuilder).AddWheels(wBuilder).AddEngine(eBuilder).BuildCar(); But what I need is a special sequence or workflow: I can only build the wheels on top of the frame and when the wheels exist then I'll be able to build up the engine. So instead of offering every method of the car builder I want to be able to add only the frame to the builder and then only the wheels to the frame and then the engine on top of that... And how would it be or what would be a good implementation if the EngineBuilder itself has a fluent api like eBuilder.Cylinders(12).WithPistons().... Would it be possible to have something like this Car c = builder.AddFrame(fBuilder).AddWheels(wBuilder).AddEngine(x=>x.WithCylinders(12).WithPistons()).BuildCar(); So in sum how to structure the flow of the fluent interface and how to nest fluent Interfaces?

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• Forward declaration of derived inner class

  - by Loom

  I ran into problem implementing some variations of factory method. // from IFoo.h struct IFoo { struct IBar { virtual ~IBar() = 0; virtual void someMethod() = 0; }; virtual IBar *createBar() = 0; }; // from Foo.h struct Foo : IFoo { // implementation of Foo, Bar in Foo.cpp struct Bar : IBar { virtual ~Bar(); virtual void someMethod(); }; virtual Bar *createBar(); // implemented in Foo.cpp }; I'd like to place declaration of Foo::Bar in Foo.cpp. For now I cannot succeed: struct Foo : IFoo { //struct Bar; //1. error: invalid covariant return type // for ‘virtual Foo::Bar* //struct Bar : IBar; //2. error: expected ‘{’ before ‘;’ token virtual Bar *createBar(); // virtual IBar *createBar(); // Is not acceptable by-design }; Is there a trick to have just forward declaration of Boo in Foo.hpp and to have full declaration in Foo.cpp?

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• Polymorphic Queue

  - by metdos

  Hello Everyone, I'm trying to implement a Polymorphic Queue. Here is my trial: QQueue <Request *> requests; while(...) { QString line = QString::fromUtf8(client->readLine()).trimmed(); if(...)){ Request *request=new Request(); request->tcpMessage=line.toUtf8(); request->decodeFromTcpMessage(); //this initialize variables in request using tcpMessage if(request->requestType==REQUEST_LOGIN){ LoginRequest loginRequest; request=&loginRequest; request->tcpMessage=line.toUtf8(); request->decodeFromTcpMessage(); requests.enqueue(request); } //Here pointers in "requests" do not point to objects I created above, and I noticed that their destructors are also called. LoginRequest *loginRequest2=dynamic_cast<LoginRequest *>(requests.dequeue()); loginRequest2->decodeFromTcpMessage(); } } Unfortunately, I could not manage to make work Polymorphic Queue with this code because of the reason I mentioned in second comment.I guess, I need to use smart-pointers, but how? I'm open to any improvement of my code or a new implementation of polymorphic queue. Thanks.

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• cocoa hello world screensaver

  - by RW

  I have been studying NSView and as such I thought I would give a shot at a screen saver. I have been able to display and image in an NSView but I can't seen to modify this example code to display a simple picture in ScreenSaverView. http://www.mactech.com/articles/mactech/Vol.20/20.06/ScreenSaversInCocoa/ BTW great tutorial that works with Snow Leopard. I would think to simply display an image I would need something that looked like this... What am I doing wrong? // // try_screensaverView.m // try screensaver // #import "try_screensaverView.h" @implementation try_screensaverView - (id)initWithFrame:(NSRect)frame isPreview:(BOOL)isPreview { self = [super initWithFrame:frame isPreview:isPreview]; if (self) { [self setAnimationTimeInterval:1]; //refresh once per sec } return self; } - (void)startAnimation { [super startAnimation]; NSString *path = [[NSBundle mainBundle] pathForResource:@"leaf" ofType:@"JPG" inDirectory:@""]; image = [[NSImage alloc] initWithContentsOfFile:path]; } - (void)stopAnimation { [super stopAnimation]; } - (void)drawRect:(NSRect)rect { [super drawRect:rect]; } - (void)animateOneFrame { ////////////////////////////////////////////////////////// //load image and display This does not scale the image NSRect bounds = [self bounds]; NSSize newSize; newSize.width = bounds.size.width; newSize.height = bounds.size.height; [image setSize:newSize]; NSRect imageRect; imageRect.origin = NSZeroPoint; imageRect.size = [image size]; NSRect drawingRect = imageRect; [image drawInRect:drawingRect fromRect:imageRect operation:NSCompositeSourceOver fraction:1]; } - (BOOL)hasConfigureSheet { return NO; } - (NSWindow*)configureSheet { return nil; } @end

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• Listing serial (COM) ports on Windows?

  - by Eli Bendersky

  Hello, I'm looking for a robust way to list the available serial (COM) ports on a Windows machine. There's this post about using WMI, but I would like something less .NET specific - I want to get the list of ports in a Python or a C++ program, without .NET. I currently know of two other approaches: Reading the information in the HARDWARE\\DEVICEMAP\\SERIALCOMM registry key. This looks like a great option, but is it robust? I can't find a guarantee online or in MSDN that this registry cell indeed always holds the full list of available ports. Tryint to call CreateFile on COMN with N a number from 1 to something. This isn't good enough, because some COM ports aren't named COMN. For example, some virtual COM ports created are named CSNA0, CSNB0, and so on, so I wouldn't rely on this method. Any other methods/ideas/experience to share? Edit: by the way, here's a simple Python implementation of reading the port names from registry: import _winreg as winreg import itertools def enumerate_serial_ports(): """ Uses the Win32 registry to return a iterator of serial (COM) ports existing on this computer. """ path = 'HARDWARE\\DEVICEMAP\\SERIALCOMM' try: key = winreg.OpenKey(winreg.HKEY_LOCAL_MACHINE, path) except WindowsError: raise IterationError for i in itertools.count(): try: val = winreg.EnumValue(key, i) yield (str(val[1]), str(val[0])) except EnvironmentError: break

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• Calculate an Internet (aka IP, aka RFC791) checksum in C#

  - by Pat

  Interestingly, I can find implementations for the Internet Checksum in almost every language except C#. Does anyone have an implementation to share? Remember, the internet protocol specifies that: "The checksum field is the 16 bit one's complement of the one's complement sum of all 16 bit words in the header. For purposes of computing the checksum, the value of the checksum field is zero." More explanation can be found from Dr. Math. There are some efficiency pointers available, but that's not really a large concern for me at this point. Please include your tests! (Edit: Valid comment regarding testing someone else's code - but I am going off of the protocol and don't have test vectors of my own and would rather unit test it than put into production to see if it matches what is currently being used! ;-) Edit: Here are some unit tests that I came up with. They test an extension method which iterates through the entire byte collection. Please comment if you find fault in the tests. [TestMethod()] public void InternetChecksum_SimplestValidValue_ShouldMatch() { IEnumerable<byte> value = new byte[1]; // should work for any-length array of zeros ushort expected = 0xFFFF; ushort actual = value.InternetChecksum(); Assert.AreEqual(expected, actual); } [TestMethod()] public void InternetChecksum_ValidSingleByteExtreme_ShouldMatch() { IEnumerable<byte> value = new byte[]{0xFF}; ushort expected = 0xFF; ushort actual = value.InternetChecksum(); Assert.AreEqual(expected, actual); } [TestMethod()] public void InternetChecksum_ValidMultiByteExtrema_ShouldMatch() { IEnumerable<byte> value = new byte[] { 0x00, 0xFF }; ushort expected = 0xFF00; ushort actual = value.InternetChecksum(); Assert.AreEqual(expected, actual); }

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• Why won't my CATiledLayer scroll in a UIScrollView after zooming?

  - by Brodie4598

  I'm currently having the following problem with CATiledLayer: when the view first loads, the scrolling works perfectly, but then when you zoom once, the view snaps to the anchor point (top left corner) and it can no longer scroll at all. The zooming works in that it will zoom in and out, but it will only zoom to the top left corner. My code is as follows: #import <QuartzCore/QuartzCore.h> #import "PracticeViewController.h" @implementation practiceViewController //@synthesize image; - (void)viewDidLoad { NSString *path = [[NSBundle mainBundle] pathForResource:@"H-5" ofType:@"jpg"]; NSData *data = [NSData dataWithContentsOfFile:path]; image = [UIImage imageWithData:data]; CGRect pageRect = CGRectMake(0, 0, image.size.width, image.size.height); CATiledLayer *tiledLayer = [CATiledLayer layer]; tiledLayer.anchorPoint = CGPointMake(0.0f, 1.0f); tiledLayer.delegate = self; tiledLayer.tileSize = CGSizeMake(1000, 1000); tiledLayer.levelsOfDetail = 6; tiledLayer.levelsOfDetailBias = 0; tiledLayer.bounds = pageRect; tiledLayer.transform = CATransform3DMakeScale(1.0f, -1.0f, 0.3f); myContentView = [[UIView alloc] initWithFrame:self.view.bounds]; [myContentView.layer addSublayer:tiledLayer]; UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds]; scrollView.delegate = self; scrollView.contentSize = pageRect.size; scrollView.minimumZoomScale = .2; scrollView.maximumZoomScale = 1; [scrollView addSubview:myContentView]; [self.view addSubview:scrollView]; } - (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView { return myContentView; } - (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx { NSString *path = [[NSBundle mainBundle] pathForResource:@"H-5" ofType:@"jpg"]; NSData *data = [NSData dataWithContentsOfFile:path]; image = [UIImage imageWithData:data]; CGRect imageRect = CGRectMake (0.0, 0.0, image.size.width, image.size.height); CGContextDrawImage (ctx, imageRect, [image CGImage]); } @end

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• Why do System.IO.Log SequenceNumbers have variable length?

  - by Doug McClean

  I'm trying to use the System.IO.Log features to build a recoverable transaction system. I understand it to be implemented on top of the Common Log File System. The usual ARIES approach to write-ahead logging involves persisting log record sequence numbers in places other than the log (for example, in the header of the database page modified by the logged action). Interestingly, the documentation for CLFS says that such sequence numbers are always 64-bit integers. Confusingly, however, the .Net wrapper around those SequenceNumbers can be constructed from a byte[] but not from a UInt64. It's value can also be read as a byte[], but not as a UInt64. Inspecting the implementation of SequenceNumber.GetBytes() reveals that it can in fact return arrays of either 8 or 16 bytes. This raises a few questions: Why do the .Net sequence numbers differ in size from the CLFS sequence numbers? Why are the .Net sequence numbers variable in length? Why would you need 128 bits to represent such a sequence number? It seems like you would truncate the log well before using up a 64-bit address space (16 exbibytes, or around 10^19 bytes, more if you address longer words)? If log sequence numbers are going to be represented as 128 bit integers, why not provide a way to serialize/deserialize them as pairs of UInt64s instead of rather-pointlessly incurring heap allocations for short-lived new byte[]s every time you need to write/read one? Alternatively, why bother making SequenceNumber a value type at all? It seems an odd tradeoff to double the storage overhead of log sequence numbers just so you can have an untruncated log longer than a million terabytes, so I feel like I'm missing something here, or maybe several things. I'd much appreciate it if someone in the know could set me straight.

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• C++ find largest BST in a binary tree

  - by fonjibe

  what is your approach to have the largest BST in a binary tree? I refer to this post where a very good implementation for finding if a tree is BST or not is bool isBinarySearchTree(BinaryTree * n, int min=std::numeric_limits<int>::min(), int max=std::numeric_limits<int>::max()) { return !n || (min < n->value && n->value < max && isBinarySearchTree(n->l, min, n->value) && isBinarySearchTree(n->r, n->value, max)); } It is quite easy to implement a solution to find whether a tree contains a binary search tree. i think that the following method makes it: bool includeSomeBST(BinaryTree* n) { if(!isBinarySearchTree(n)) { if(!isBinarySearchTree(n->left)) return isBinarySearchTree(n->right); } else return true; else return true; } but what if i want the largest BST? this is my first idea, BinaryTree largestBST(BinaryTree* n) { if(isBinarySearchTree(n)) return n; if(!isBinarySearchTree(n->left)) { if(!isBinarySearchTree(n->right)) if(includeSomeBST(n->right)) return largestBST(n->right); else if(includeSomeBST(n->left)) return largestBST(n->left); else return NULL; else return n->right; } else return n->left; } but its not telling the largest actually. i struggle to make the comparison. how should it take place? thanks

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• The rightCalloutAccessory button is not shown

  - by Luca

  I try to manage annotations, and to display an info button on the right of the view when a PIN get selected, my relevant code is this: - (MKAnnotationView *)mapView:(MKMapView *)map viewForAnnotation:(id <MKAnnotation>)annotation { MKPinAnnotationView *newAnnotation = [[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"greenPin"]; if ([annotation isKindOfClass:[ManageAnnotations class]]) { static NSString* identifier = @"ManageAnnotations"; MKPinAnnotationView *newAnnotation = [[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:identifier]; if (newAnnotation==nil) { newAnnotation=[[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:identifier]; }else { newAnnotation.annotation=annotation; } newAnnotation.pinColor = MKPinAnnotationColorGreen; newAnnotation.animatesDrop = YES; newAnnotation.canShowCallout = YES; newAnnotation.rightCalloutAccessoryView=[UIButton buttonWithType:UIButtonTypeInfoLight]; return newAnnotation; }else { newAnnotation.pinColor = MKPinAnnotationColorGreen; newAnnotation.animatesDrop = YES; newAnnotation.canShowCallout = YES; return newAnnotation; } ManageAnnotations.m : @implementation ManageAnnotations @synthesize pinColor; @synthesize storeName=_storeName; @synthesize storeAdress=_storeAdress; @synthesize coordinate=_coordinate; -(id)initWithTitle:(NSString*)storeName adress:(NSString*)storeAdress coordinate:(CLLocationCoordinate2D)coordinate{ if((self=[super init])){ _storeName=[storeName copy]; _storeAdress=[storeAdress copy]; _coordinate=coordinate; } return self; } -(NSString*)title{ return _storeName; } -(NSString*)subtitle{ return _storeAdress; } ManageAnnotations.h @interface ManageAnnotations : NSObject<MKAnnotation>{ NSString *_storeName; NSString *_storeAdress; CLLocationCoordinate2D _coordinate; } // @property(nonatomic,assign)MKPinAnnotationColor pinColor; @property(nonatomic, readonly, copy)NSString *storeName; @property(nonatomic, readonly, copy)NSString *storeAdress; @property(nonatomic,readonly)CLLocationCoordinate2D coordinate; // -(id)initWithTitle:(NSString*)storeName adress:(NSString*)storeAdress coordinate:(CLLocationCoordinate2D)coordinate; // The PINS are shown correctly on the Map, but without the info button on the right of the view. Am i missing something?

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