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• Why doesn't my cursor change to an Hourglass in my FindDialog in Delphi?

  - by lkessler

  I am simply opening my FindDialog with: FindDialog.Execute; In my FindDialog.OnFind event, I want to change the cursor to an hourglass for searches through large files, which may take a few seconds. So in the OnFind event I do this: Screen.Cursor := crHourglass; (code that searches for the text and displays it) ... Screen.Cursor := crDefault; What happens is while searching for the text, the cursor properly changes to the hourglass (or rotating circle in Vista) and then back to the pointer when the search is completed. However, this only happens on the main form. It does not happen on the FindDialog itself. The default cursor remains on the FindDialog during the search. While the search is happening if I move the cursor over the FindDialog it changes to the default, and if I move it off and over the main form it becomes the hourglass. This does not seem like what is supposed to happen. Am I doing something wrong or does something special need to be done to get the cursor to be the hourglass on all forms? For reference, I'm using Delphi 2009.

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• Call dll - pcshll32.dll using delphi

  - by Davis

  Hi, I need to call hllapi function of pcshll32.dll using delphi. It's works with personal communications of ibm. How can i change the code bellow to delphi ? Thanks !!! The EHLLAPI entry point (hllapi) is always called with the following four parameters: EHLLAPI Function Number (input) Data Buffer (input/output) Buffer Length (input/output) Presentation Space Position (input); Return Code (output) The prototype for IBM Standard EHLLAPI is: [long hllapi (LPWORD, LPSTR, LPWORD, LPWORD); The prototype for IBM Enhanced EHLLAPI is: [long hllapi (LPINT, LPSTR, LPINT, LPINT); Each parameter is passed by reference not by value. Thus each parameter to the function call must be a pointer to the value, not the value itself. For example, the following is a correct example of calling the EHLLAPI Query Session Status function: #include "hapi_c.h" struct HLDQuerySessionStatus QueryData; int Func, Len, Rc; long Rc; memset(QueryData, 0, sizeof(QueryData)); // Init buffer QueryData.qsst_shortname = ©A©; // Session to query Func = HA_QUERY_SESSION_STATUS; // Function number Len = sizeof(QueryData); // Len of buffer Rc = 0; // Unused on input hllapi(&Func, (char *)&QueryData, &Len, &Rc); // Call EHLLAPI if (Rc != 0) { // Check return code // ...Error handling } All the parameters in the hllapi call are pointers and the return code of the EHLLAPI function is returned in the value of the 4th parameter, not as the value of the function.

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• Hooking thread exit

  - by mackenir

  Is there a way for me to hook the exit of managed threads (i.e. run some code on a thread, just before it exits?) I've developed a mechanism for hooking thread exit that works for some threads. Step 1: develop a 'hook' STA COM class that takes a callback function and calls it in its destructor. Step 2: create a ThreadStatic instance of this object on the thread I want to hook, and pass the object a managed delegate converted to an unmanaged function pointer. The delegate then gets called on thread exit (since the CLR calls IUnknown::Release on all STA COM RCWs as part of thread exit). This mechanism works on, for example, worker threads that I create in code using the Thread class. However, it doesn't seem to work for the application's main thread (be it a console or windows app). The 'hook' COM object seems to be deleted too late in the shutdown process and the attempt to call the delegate fails. (The reason I want to implement this facility is so I can run some native COM code on the exiting thread that works with STA COM objects that were created on the thread, before it's 'too late' (i.e. before the thread has exited, and it's no longer possible to work with STA COM objects on that thread.))

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• STLport crash (race condition, Darwin only?)

  - by Jonas Byström

  When I run STLport on Darwin I get a strange crash. (Haven't seen it anywhere else than on Mac, but exactly same thing crash on both i686 and PowerPC.) This is what it looks like in gdb: Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: 13 at address: 0x0000000000000000 [Switching to process 21097] 0x000000010120f47c in stlp_std::__node_alloc_impl::_M_allocate () It may be some setting in STLport, I noticed that Mac.h and MacOSX.h seemed far behind on features. I also know that it it must be some type of race condition, since it doesn't occur just by calling this method (implicity called). The crash happens mainly when I push the system, running 10 simultaneous threads that do a lot of string handling. Other theories I come up with have to do with compiler flags (configure script) and g++ 4.2 bugs (seems like 4.4.3 isn't on Mac yet with Objective-C support, which I need to link with). HELP!!! :) Edit: I run unit tests, which do all sorts of things. This problem arise when I start 10 threads that push the system; and it always comes down to std::string::append which eventually boils down to _M_allocate. Since I can't even get a descent dump of the code that's causing the problem, I figure I'm doing something bad. Could it be so since it's trying to execute at instruction pointer 0x000...000? Are dynlibs built as DLLs in Windows with a jump table? Could it perhaps be that such a jump table has been overwritten for some reason? That would probably explain this behavior. (The code is huge, if I run out of other ideas, I'll post a minimum crashing sample here.)

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• realloc() & ARC

  - by RynoB

  How would I be able to rewrite the the following utility class to get all the class string values for a specific type - using the objective-c runtime functions as shown below? The ARC documentation specifically states that realloc should be avoided and I also get the following compiler error on this this line: classList = realloc(classList, sizeof(Class) * numClasses); "Implicit conversion of a non-Objective-C pointer type 'void *' to '__unsafe_unretained Class *' is disallowed with ARC" The the below code is a reference to the original article which can be found here. + (NSArray *)classStringsForClassesOfType:(Class)filterType { int numClasses = 0, newNumClasses = objc_getClassList(NULL, 0); Class *classList = NULL; while (numClasses < newNumClasses) { numClasses = newNumClasses; classList = realloc(classList, sizeof(Class) * numClasses); newNumClasses = objc_getClassList(classList, numClasses); } NSMutableArray *classesArray = [NSMutableArray array]; for (int i = 0; i < numClasses; i++) { Class superClass = classList[i]; do { superClass = class_getSuperclass(superClass); if (superClass == filterType) { [classesArray addObject:NSStringFromClass(classList[i])]; break; } } while (superClass); } free(classList); return classesArray; } Your help will be much appreciated. Thanks

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• Deriving an HTMLElement Object from jQuery Object

  - by Jasconius

  I'm doing a fairly exhaustive series of DOM manipulations where a few elements (specifically form elements) have some events. I am dynamically creating (actually cloning from a source element) several boxes and assigning a change() event to them. The change event executes, and within the context of the event, "this" is the HTML Element Object. What I need to do at this point however is determine a contact for this HTML Element Object. I have these objects stored already as jQuery entities in assorted arrays, but obviously [HTMLElement Object] != [Object Object] And the trick is that I cannot cast $(this) and make a valid comparison since that would create a new object and the pointer would be different. So... I've been banging my head against this for a while. In the past I've been able to circumvent this problem by doing an innerHTML comparison, but in this case the objects I am comparing are 100% identical, just there's lots of them. Therefore I need a solid comparison. This would be easy if I could somehow derive the HTMLElement object from my originating jQuery object. Thoughts, other ideas? Help. :(

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• Windows Programming: ID2D1Bitmap Interface - Getting the Bitmap Data

  - by LostInBrackets

  I've been writing my own library of functions to access some of the new Direct2D Windows libraries. In particular, I've been working on the ID2D1Bitmap interface. I wanted to write a function to return a pointer to the start of the bitmap data (for the editing of particular pixels, or custom encoding or whatever else I might wish for in the future). Unfortunately... problem ahead... I can't seem to find a way to get access to the raw pixel data from the ID2D1Bitmap Interface. Does anyone have an idea how to access this? One of my friends suggested drawing the bitmap to a surface and extracting the bitmap data from there. I don't know if this would work. It definitely seems inefficient and I wouldn't know which kind of surface to use. Any help is appreciated. (c++ in particular, but I assume the code won't be tooo different between languages) (I know I could just read in the data direct from the file, but I'm using the WIC decoders which means it could be in any number of indecipherable formats)

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• Compiler optimization causing the performance to slow down

  - by aJ

  I have one strange problem. I have following piece of code: template<clss index, class policy> inline int CBase<index,policy>::func(const A& test_in, int* srcPtr ,int* dstPtr) { int width = test_in.width(); int height = test_in.height(); double d = 0.0; //here is the problem for(int y = 0; y < height; y++) { //Pointer initializations //multiplication involving y //ex: int z = someBigNumber*y + someOtherBigNumber; for(int x = 0; x < width; x++) { //multiplication involving x //ex: int z = someBigNumber*x + someOtherBigNumber; if(soemCondition) { // floating point calculations } *dstPtr++ = array[*srcPtr++]; } } } The inner loop gets executed nearly 200,000 times and the entire function takes 100 ms for completion. ( profiled using AQTimer) I found an unused variable double d = 0.0; outside the outer loop and removed the same. After this change, suddenly the method is taking 500ms for the same number of executions. ( 5 times slower). This behavior is reproducible in different machines with different processor types. (Core2, dualcore processors). I am using VC6 compiler with optimization level O2. Follwing are the other compiler options used : -MD -O2 -Z7 -GR -GX -G5 -X -GF -EHa I suspected compiler optimizations and removed the compiler optimization /O2. After that function became normal and it is taking 100ms as old code. Could anyone throw some light on this strange behavior? Why compiler optimization should slow down performance when I remove unused variable ? Note: The assembly code (before and after the change) looked same.

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• Does GC guarantee that cleared References are enqueued to ReferenceQueue in topological order?

  - by Dimitris Andreou

  Say there are two objects, A and B, and there is a pointer A.x --> B, and we create, say, WeakReferences to both A and B, with an associated ReferenceQueue. Assume that both A and B become unreachable. Intuitively B cannot be considered unreachable before A is. In such a case, do we somehow get a guarantee that the respective references will be enqueued in the intuitive (topological when there are no cycles) order in the ReferenceQueue? I.e. ref(A) before ref(B). I don't know - what if the GC marked a bunch of objects as unreachable, and then enqueued them in no particular order? I was reviewing Finalizer.java of guava, seeing this snippet: private void cleanUp(Reference<?> reference) throws ShutDown { ... if (reference == frqReference) { /* * The client no longer has a reference to the * FinalizableReferenceQueue. We can stop. */ throw new ShutDown(); } frqReference is a PhantomReference to the used ReferenceQueue, so if this is GC'ed, no Finalizable{Weak, Soft, Phantom}References can be alive, since they reference the queue. So they have to be GC'ed before the queue itself can be GC'ed - but still, do we get the guarantee that these references will be enqueued to the ReferenceQueue at the order they get "garbage collected" (as if they get GC'ed one by one)? The code implies that there is some kind of guarantee, otherwise unprocessed references could theoretically remain in the queue. Thanks

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• AST with fixed nodes instead of error nodes in antlr

  - by ahe

  I have an antlr generated Java parser that uses the C target and it works quite well. The problem is I also want it to parse erroneous code and produce a meaningful AST. If I feed it a minimal Java class with one import after which a semicolon is missing it produces two "Tree Error Node" objects where the "import" token and the tokens for the imported class should be. But since it parses the following code correctly and produces the correct nodes for this code it must recover from the error by adding the semicolon or by resyncing. Is there a way to make antlr reflect this fixed input it produces internally in the AST? Or can I at least get the tokens/text that produced the "Tree Node Errors" somehow? In the C targets antlr3commontreeadaptor.c around line 200 the following fragment indicates that the C target only creates dummy error nodes so far: static pANTLR3_BASE_TREE errorNode (pANTLR3_BASE_TREE_ADAPTOR adaptor, pANTLR3_TOKEN_STREAM ctnstream, pANTLR3_COMMON_TOKEN startToken, pANTLR3_COMMON_TOKEN stopToken, pANTLR3_EXCEPTION e) { // Use the supplied common tree node stream to get another tree from the factory // TODO: Look at creating the erronode as in Java, but this is complicated by the // need to track and free the memory allocated to it, so for now, we just // want something in the tree that isn't a NULL pointer. // return adaptor->createTypeText(adaptor, ANTLR3_TOKEN_INVALID, (pANTLR3_UINT8)"Tree Error Node"); } Am I out of luck here and only the error nodes the Java target produces would allow me to retrieve the text of the erroneous nodes?

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• function's return address is different from its supposed value, buffer overflow,

  - by ultrajohn

  Good day everyone! I’m trying to understand how buffer overflow works. I’m doing this for my project in a computer security course I’m taking. Right now, I’m in the process of determining the address of the function’s return address which I’m supposed to change to perform a buffer overflow attack. I’ve written a simple program based from an example I’ve read in the internet. What this program does is it creates an integer pointer that will be made to point to the address of the function return address in the stack. To do this, (granted I understand how a function/program variables get organized in the stack), I add 8 to the buffer variable’ address and set it as the value of ret. I’m not doing anything here that would change the address contained in the location of func’s return address. here's the program: Output of the program when gets excecuted: As you can see, I’m printing the address of the variables buffer and ret. I’ve added an additional statement printing the value of the ret variable (supposed location of func return address, so this should print the address of the next instruction which will get executed after func returns from execution). Here is the dump which shows the supposed address of the instruction to be executed after func returns. (Underlined in green) As you can see, that value is way different from the value printed contained in the variable ret. My question is, why are they different? (of course in the assumption that what I’ve done are all right). Else, what have I done wrong? Is my understanding of the program’s runtime stack wrong? Please, help me understand this. My project is due nextweek and I’ve barely touched it yet. I’m sorry if I’m being demanding, I badly need your help.

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• Do overlays/tooltips work correctly in Emacs for Windows?

  - by Cheeso

  I'm using Flymake on C# code, emacs v22.2.1 on Windows. The Flymake stuff has been working well for me. For those who don't know, you can read an overview of flymake, but the quick story is that flymake repeatedly builds the source file you are currently working on in the background, for the purpose of doing syntax checking. It then highlights the compiler warnings and erros in the current buffer. Flymake didn't work for C# initially, but I "monkey-patched it" and it works nicely now. If you edit C# in emacs, I highly recommend using flymake. The only problem I have is with the UI. Flymake highlights the errors and warnings nicely, and then inserts "overlays" with the full error or warning text. IF I hover the mouse pointer over the highlighted line in code, the overlay pops up. But as you can see, the overlay (tooltip) is truncated, and it doesn't display correctly. Flymake seems to be doing the right thing, it's the overlay part that seems broken., and overlay seems to do the right thing. It's the tooltip that is displayed incorrectly. Do overlays tooltips work correctly in emacs for Windows? Where do I look to fix this?

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• Unhandled Exception with c++ app on Visual Studio 2008 release build - occurs when returning from fu

  - by Rich

  Hi, I have a (rather large) application that I have written in C++ and until recently it has been running fine outside of visual studio from the release build. However, now, whenever I run it it says "Unhandled exception at 0x77cf205b in myprog.exe: 0xC0000005: Access violation writing location 0x45000200.", and leads me to "crtexe.c" at line 582 ("mainret = main(argc, argv, envp);") if I attempt to debug it. Note that this problem never shows if I run my debug executable outside of visual studio, or if I run my debug or release build within visual studio. It only happens when running the release build outside of visual studio. I have been through and put plenty of printfs and a couple of while(1)s in it to see when it actually crashed, and found that the access violation occurs at exactly the point that the value is returned from the function (I'm returning a pointer to an object). I don't fully understand why I would get an access violation at the point it returns, and it doesn't seem to matter what I'm returning as it still occurs when I return 0. The point it started crashing was when I added a function which does a lot of reading from a file using ifstream. I am opening the stream every time I attempt to read a new file and close it when I finish reading it. If I keep attempting to run it, it will run once in about 20 tries. It seems a lot more reliable if I run it off my pen drive (it seems to crash the first 3 or 4 times then run fine after that - maybe it's due to its slower read speed). Thanks for your help, and if I've missed anything let me know.

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• segmentation fault on Unix - possible stack corruption

  - by bob

  hello, i'm looking at a core from a process running in Unix. Usually I can work my around and root into the backtrace to try identify a memory issue. In this case, I'm not sure how to proceed. Firstly the backtrace only gives 3 frames where I would expect alot more. For those frames, all the function parameters presented appears to completely invalid. There are not what I would expect. Some pointer parameters have the following associated with them - Cannot access memory at address Would this suggest some kind of complete stack corruption. I ran the process with libumem and all the buffers were reported as being clean. umem_status reported nothing either. so basically I'm stumped. What is the likely causes? What should I look for in code since libumem appears to have reported no errors. Any suggestions on how I can debug furhter? any extra features in mdb I should consider? thank you.

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• TableView Cells unresponsive

  - by John Donovan

  I have a TableView and I wish to be able to press several cells one after the other and have messages appear. At the moment the cells are often unresponsive. I found some coed for a similar problem someone was kind enough to post, however, although he claimed it worked 100% it doesn't work for me. The app won't even build. Here's the code: -(UIView*) hitTest:(CGPoint)point withEvent:(UIEvent*)event { // check to see if the hit is in this table view if ([self pointInside:point withEvent:event]) { UITableViewCell* newCell = nil; // hit is in this table view, find out // which cell it is in (if any) for (UITableViewCell* aCell in self.visibleCells) { if ([aCell pointInside:[self convertPoint:point toView:aCell] withEvent:nil]) { newCell = aCell; break; } } // if it touched a different cell, tell the previous cell to resign // this gives it a chance to hide the keyboard or date picker or whatever if (newCell != activeCell) { [activeCell resignFirstResponder]; self.activeCell = newCell; // may be nil } } // return the super's hitTest result return [super hitTest:point withEvent:event]; } With this code I get this warning: that my viewController may not respond to pointsInside:withEvent (it's a TableViewController). I also get some faults: request for member 'visibleCells' in something not a structure or a union. incompatible type for argument 1 of pointInsideWithEvent, expression does not have a valid object type and similar. I must admit I'm not so good at reading other people's code but I was wondering whether the problems here are obvious and if so if anyone could give me a pointer it would be greatly appreciated.

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• Where's the Win32 resource for the mouse cursor for dragging splitters?

  - by Luther Baker

  I am building a custom win32 control/widget and would like to change the cursor to a horizontal "splitter" symbol when hovering over a particular vertical line in the control. IE: I want to drag this vertical line (splitter bar) left and right (WEST and EAST). Of the the system cursors (OCR_*), the only cursor that makes sense is the OCR_SIZEWE. Unfortunately, that is the big, awkward cursor the system uses when resizing a window. Instead, I am looking for the cursor that is about 20 pixels tall and around 3 or 4 pixel wide with two small arrows pointing left and right. I can easily draw this and include it as a resource in my application but the cursor itself is so prevalent that I wanted to be sure it wasn't missing something. For example: when you use the COM drag and drop mechanism (CLSID_DragDropHelper, IDropTarget, etc) you implicitly have access to the "drag" icon (little box under the pointer). I didn't see an explicit OCR_* constant for this guy ... so likewise, if I can't find this splitter cursor outright, I am wondering if it is part of a COM object or something else in the win32 lib.

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• How does virtual inheritance solve the diamond problem?

  - by cambr

  class A { public: void eat(){ cout<<"A";} }; class B: virtual public A { public: void eat(){ cout<<"B";} }; class C: virtual public A { public: void eat(){ cout<<"C";} }; class D: public B,C { public: void eat(){ cout<<"D";} }; int main(){ A *a = new D(); a->eat(); } I understand the diamond problem, and above piece of code does not have that problem. How exatly does virtual inheritance solve the problem? What I understand: When I say A *a = new D();, the compiler wants to know if an object of type D can be assigned to a pointer of type A, but it has two paths that it can follow, but cannot decide by itself. So, how does virtual inheritance resolve the issue (help compiler take the decision)?

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• Replacing/Extending Visual Studio's Generate Stub in Visual Studio 2010

  - by devoured elysium

  When we write the name of a method that doesn't exist, Visual Studio 2010 asks us if we'd like to generate a method stub with that name. What I'd like to know if is it possible to replace that same code stub generating command with one made by myself. I never did any kind of extensibility programming for Visual Studio so I have a couple of questions: How hard is it? Is it something I can learn in a couple of nights, or is it something that'll make me "lose" a lot of time? It seems to me that there isn't a lot of support for that kind of programming, as generally people are not that interested in developing solutions that extend the Visual Studio IDE. I searched on SO and it doesn't appear to have many threads about extending Visual Studio. I don't know how the generate method stub thing works in Visual Studio, but I just wanted to turn it into something a bit more flexible and useful. Has anyone dealt with these kind of things before, that can give me a pointer to where to start? I know of MS VSX site but that has a lot of resources and can be overwhelming for someone new to the subject as I am. What technology will I need to use? T4? Maybe I'll need to know a lot about the code, like Visual Studio does, so I can know other method's type arguments, names, etc. Is that what T4 is for? Thanks

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• How to select and crop an image in android?

  - by Guy

  Hey, I am currently working on a live wallpaper and I allow the user to select an image which will go behind my effects. Currently I have: Intent i = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI); i.putExtra("crop", "true"); startActivityForResult(i, 1); And slightly under that: @Override public void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); if (requestCode == 1) if (resultCode == Activity.RESULT_OK) { Uri selectedImage = data.getData(); Log.d("IMAGE SEL", "" + selectedImage); // TODO Do something with the select image URI SharedPreferences customSharedPreference = getSharedPreferences("imagePref", Activity.MODE_PRIVATE); SharedPreferences.Editor editor = customSharedPreference.edit(); Log.d("HO", "" + selectedImage); editor.putString("imagePref", getRealPathFromURI(selectedImage)); Log.d("IMAGE SEL", getRealPathFromURI(selectedImage)); editor.commit(); } } When my code is ran, Logcat tells me that selectedImage is null. If I comment out the i.putExtra("crop", "true"): Logcat does not give me the null pointer exception, and I am able to do what I want with the image. So, what is the problem here? Does any one have any idea how I can fix this? Thanks, for your time.

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• How to mmap the stack for the clone() system call on linux?

  - by Joseph Garvin

  The clone() system call on Linux takes a parameter pointing to the stack for the new created thread to use. The obvious way to do this is to simply malloc some space and pass that, but then you have to be sure you've malloc'd as much stack space as that thread will ever use (hard to predict). I remembered that when using pthreads I didn't have to do this, so I was curious what it did instead. I came across this site which explains, "The best solution, used by the Linux pthreads implementation, is to use mmap to allocate memory, with flags specifying a region of memory which is allocated as it is used. This way, memory is allocated for the stack as it is needed, and a segmentation violation will occur if the system is unable to allocate additional memory." The only context I've ever heard mmap used in is for mapping files into memory, and indeed reading the mmap man page it takes a file descriptor. How can this be used for allocating a stack of dynamic length to give to clone()? Is that site just crazy? ;) In either case, doesn't the kernel need to know how to find a free bunch of memory for a new stack anyway, since that's something it has to do all the time as the user launches new processes? Why does a stack pointer even need to be specified in the first place if the kernel can already figure this out?

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• Passing VB Callback function to C dll - noob is stuck.

  - by WaveyDavey

  Callbacks in VB (from C dll). I need to pass a vb function as a callback to a c function in a dll. I know I need to use addressof for the function but I'm getting more and more confused as to how to do it. Details: The function in the dll that I'm passing the address of a callback to is defined in C as : PaError Pa_OpenStream( PaStream** stream, const PaStreamParameters *inputParameters, const PaStreamParameters *outputParameters, double sampleRate, unsigned long framesPerBuffer, PaStreamFlags streamFlags, PaStreamCallback *streamCallback, void *userData ); where the function is parameter 7, *streamCallback. The type PaStreamCallback is defines thusly: typedef int PaStreamCallback( const void *input, void *output, unsigned long frameCount, const PaStreamCallbackTimeInfo* timeInfo, PaStreamCallbackFlags statusFlags, void *userData ); In my vb project I have: Private Declare Function Pa_OpenStream Lib "portaudio_x86.dll" _ ( ByVal stream As IntPtr _ , ByVal inputParameters As IntPtr _ , ByVal outputParameters As PaStreamParameters _ , ByVal samprate As Double _ , ByVal fpb As Double _ , ByVal paClipoff As Long _ , ByVal patestCallBack As IntPtr _ , ByVal data As IntPtr) As Integer (don't worry if I've mistyped some of the other parameters, I'll get to them later! Let's concentrate on the callback for now.) In module1.vb I have defined the callback function: Function MyCallback( ByVal inp As Byte, _ ByVal outp As Byte, _ ByVal framecount As Long, _ ByVal pastreamcallbacktimeinfo As Byte, _ ByVal pastreamcallbackflags As Byte, _ ByVal userdata As Byte) As Integer ' do clever things here End Function The external function in the dll is called with err = Pa_OpenStream( ptr, _ nulthing, _ outputParameters, _ SAMPLE_RATE, _ FRAMES_PER_BUFFER, _ clipoff, _ AddressOf MyCallback, _ dataptr) This is broken in the declaration of the external function - it doesn't like the type IntPtr as a function pointer for AddressOf. Can anyone show me how to implement passing this callback function please ? Many thanks David

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• Assigning a property across threads

  - by Mike

  I have set a property across threads before and I found this post http://stackoverflow.com/questions/142003/cross-thread-operation-not-valid-control-accessed-from-a-thread-other-than-the-t about getting a property. I think my issue with the code below is setting the variable to the collection is an object therefore on the heap and therefore is just creating a pointer to the same object So my question is besides creating a deep copy, or copying the collection into a different List object is there a better way to do the following to aviod the error during the for loop. Cross-thread operation not valid: Control 'lstProcessFiles' accessed from a thread other than the thread it was created on. Code: private void btnRunProcess_Click(object sender, EventArgs e) { richTextBox1.Clear(); BackgroundWorker bg = new BackgroundWorker(); bg.DoWork += new DoWorkEventHandler(bg_DoWork); bg.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bg_RunWorkerCompleted); bg.RunWorkerAsync(lstProcessFiles.SelectedItems); } void bg_DoWork(object sender, DoWorkEventArgs e) { WorkflowEngine engine = new WorkflowEngine(); ListBox.SelectedObjectCollection selectedCollection=null; if (lstProcessFiles.InvokeRequired) { // Try #1 selectedCollection = (ListBox.SelectedObjectCollection) this.Invoke(new GetSelectedItemsDelegate(GetSelectedItems), new object[] { lstProcessFiles }); // Try #2 //lstProcessFiles.Invoke( // new MethodInvoker(delegate { // selectedCollection = lstProcessFiles.SelectedItems; })); } else { selectedCollection = lstProcessFiles.SelectedItems; } // *********Same Error on this line******************** // Cross-thread operation not valid: Control 'lstProcessFiles' accessed // from a thread other than the thread it was created on. foreach (string l in selectedCollection) { if (engine.LoadProcessDocument(String.Format(@"C:\TestDirectory\{0}", l))) { try { engine.Run(); WriteStep(String.Format("Ran {0} Succussfully", l)); } catch { WriteStep(String.Format("{0} Failed", l)); } engine.PrintProcess(); WriteStep(String.Format("Rrinted {0} to debug", l)); } } } private delegate void WriteDelegate(string p); private delegate ListBox.SelectedObjectCollection GetSelectedItemsDelegate(ListBox list); private ListBox.SelectedObjectCollection GetSelectedItems(ListBox list) { return list.SelectedItems; }

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• Lua task scheduling

  - by Martin

  I've been writing some scripts for a game, the scripts are written in Lua. One of the requirements the game has is that the Update method in your lua script (which is called every frame) may take no longer than about 2-3 milliseconds to run, if it does the game just hangs. I solved this problem with coroutines, all I have to do is call Multitasking.RunTask(SomeFunction) and then the task runs as a coroutine, I then have to scatter Multitasking.Yield() throughout my code, which checks how long the task has been running for, and if it's over 2 ms it pauses the task and resumes it next frame. This is ok, except that I have to scatter Multitasking.Yield() everywhere throughout my code, and it's a real mess. Ideally, my code would automatically yield when it's been running too long. So, Is it possible to take a Lua function as an argument, and then execute it line by line (maybe interpreting Lua inside Lua, which I know is possible, but I doubt it's possible if all you have is a function pointer)? In this way I could automatically check the runtime and yield if necessary between every single line.

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• Direct invocation vs indirect invocation in C

  - by Mohit Deshpande

  I am new to C and I was reading about how pointers "point" to the address of another variable. So I have tried indirect invocation and direct invocation and received the same results (as any C/C++ developer could have predicted). This is what I did: int cost; int *cost_ptr; int main() { cost_ptr = &cost; //assign pointer to cost cost = 100; //intialize cost with a value printf("\nDirect Access: %d", cost); cost = 0; //reset the value *cost_ptr = 100; printf("\nIndirect Access: %d", *cost_ptr); //some code here return 0; //1 } So I am wondering if indirect invocation with pointers has any advantages over direct invocation or vice-versa. Some advantages/disadvantages could include speed, amount of memory consumed performing the operation (most likely the same but I just wanted to put that out there), safeness (like dangling pointers) , good programming practice, etc. 1Funny thing, I am using the GNU C Compiler (gcc) and it still compiles without the return statement and everything is as expected. Maybe because the C++ compiler will automatically insert the return statement if you forget.

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• Haskell Linear Algebra Matrix Library for Arbitrary Element Types

  - by Johannes Weiß

  I'm looking for a Haskell linear algebra library that has the following features: Matrix multiplication Matrix addition Matrix transposition Rank calculation Matrix inversion is a plus and has the following properties: arbitrary element (scalar) types (in particular element types that are not Storable instances). My elements are an instance of Num, additionally the multiplicative inverse can be calculated. The elements mathematically form a finite field (??2256). That should be enough to implement the features mentioned above. arbitrary matrix sizes (I'll probably need something like 100x100, but the matrix sizes will depend on the user's input so it should not be limited by anything else but the memory or the computational power available) as fast as possible, but I'm aware that a library for arbitrary elements will probably not perform like a C/Fortran library that does the work (interfaced via FFI) because of the indirection of arbitrary (non Int, Double or similar) types. At least one pointer gets dereferenced when an element is touched (written in Haskell, this is not a real requirement for me, but since my elements are no Storable instances the library has to be written in Haskell) I already tried very hard and evaluated everything that looked promising (most of the libraries on Hackage directly state that they wont work for me). In particular I wrote test code using: hmatrix, assumes Storable elements Vec, but the documentation states: Low Dimension : Although the dimensionality is limited only by what GHC will handle, the library is meant for 2,3 and 4 dimensions. For general linear algebra, check out the excellent hmatrix library and blas bindings I looked into the code and the documentation of many more libraries but nothing seems to suit my needs :-(. Update Since there seems to be nothing, I started a project on GitHub which aims to develop such a library. The current state is very minimalistic, not optimized for speed at all and only the most basic functions have tests and therefore should work. But should you be interested in using or helping out developing it: Contact me (you'll find my mail address on my web site) or send pull requests.

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