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• Use native HBitmap in C# while preserving alpha channel/transparency. Please check this code, it works on my computer...

  - by David

  Let's say I get a HBITMAP object/handle from a native Windows function. I can convert it to a managed bitmap using Bitmap.FromHbitmap(nativeHBitmap), but if the native image has transparency information (alpha channel), it is lost by this conversion. There are a few questions on Stack Overflow regarding this issue. Using information from the first answer of this question (How to draw ARGB bitmap using GDI+?), I wrote a piece of code that I've tried and it works. It basically gets the native HBitmap width, height and the pointer to the location of the pixel data using GetObject and the BITMAP structure, and then calls the managed Bitmap constructor: Bitmap managedBitmap = new Bitmap(bitmapStruct.bmWidth, bitmapStruct.bmHeight, bitmapStruct.bmWidth * 4, PixelFormat.Format32bppArgb, bitmapStruct.bmBits); As I understand (please correct me if I'm wrong), this does not copy the actual pixel data from the native HBitmap to the managed bitmap, it simply points the managed bitmap to the pixel data from the native HBitmap. And I don't draw the bitmap here on another Graphics (DC) or on another bitmap, to avoid unnecessary memory copying, especially for large bitmaps. I can simply assign this bitmap to a PictureBox control or the the Form BackgroundImage property. And it works, the bitmap is displayed correctly, using transparency. When I no longer use the bitmap, I make sure the BackgroundImage property is no longer pointing to the bitmap, and I dispose both the managed bitmap and the native HBitmap. The Question: Can you tell me if this reasoning and code seems correct. I hope I will not get some unexpected behaviors or errors. And I hope I'm freeing all the memory and objects correctly. private void Example() { IntPtr nativeHBitmap = IntPtr.Zero; /* Get the native HBitmap object from a Windows function here */ // Create the BITMAP structure and get info from our nativeHBitmap NativeMethods.BITMAP bitmapStruct = new NativeMethods.BITMAP(); NativeMethods.GetObjectBitmap(nativeHBitmap, Marshal.SizeOf(bitmapStruct), ref bitmapStruct); // Create the managed bitmap using the pointer to the pixel data of the native HBitmap Bitmap managedBitmap = new Bitmap( bitmapStruct.bmWidth, bitmapStruct.bmHeight, bitmapStruct.bmWidth * 4, PixelFormat.Format32bppArgb, bitmapStruct.bmBits); // Show the bitmap this.BackgroundImage = managedBitmap; /* Run the program, use the image */ MessageBox.Show("running..."); // When the image is no longer needed, dispose both the managed Bitmap object and the native HBitmap this.BackgroundImage = null; managedBitmap.Dispose(); NativeMethods.DeleteObject(nativeHBitmap); } internal static class NativeMethods { [StructLayout(LayoutKind.Sequential)] public struct BITMAP { public int bmType; public int bmWidth; public int bmHeight; public int bmWidthBytes; public ushort bmPlanes; public ushort bmBitsPixel; public IntPtr bmBits; } [DllImport("gdi32", CharSet = CharSet.Auto, EntryPoint = "GetObject")] public static extern int GetObjectBitmap(IntPtr hObject, int nCount, ref BITMAP lpObject); [DllImport("gdi32.dll")] internal static extern bool DeleteObject(IntPtr hObject); }

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• C++ scoping error

  - by Pat Murray

  I have the following code: #include "Student.h" #include "SortedList.h" using namespace std; int main() { // points to the sorted list object SortedList *list = new SortedList; //This is line 17 // array to hold 100 student objects Student create[100]; int num = 100000; // holds different ID numbers // fills an array with 100 students of various ID numbers for (Student &x : create) { x = new Student(num); num += 100; } // insert all students into the sorted list for (Student &x : create) list->insert(&x); delete list; return 0; } And I keep getting the compile time error: main.cpp: In function ‘int main()’: main.cpp:17: error: ‘SortedList’ was not declared in this scope main.cpp:17: error: ‘list’ was not declared in this scope main.cpp:17: error: expected type-specifier before ‘SortedList’ main.cpp:17: error: expected `;' before ‘SortedList’ main.cpp:20: error: ‘Student’ was not declared in this scope main.cpp:20: error: expected primary-expression before ‘]’ token main.cpp:20: error: expected `;' before ‘create’ main.cpp:25: error: expected `;' before ‘x’ main.cpp:31: error: expected primary-expression before ‘for’ main.cpp:31: error: expected `;' before ‘for’ main.cpp:31: error: expected primary-expression before ‘for’ main.cpp:31: error: expected `)' before ‘for’ main.cpp:31: error: expected `;' before ‘x’ main.cpp:34: error: type ‘<type error>’ argument given to ‘delete’, expected pointer main.cpp:35: error: expected primary-expression before ‘return’ main.cpp:35: error: expected `)' before ‘return’ My Student.cpp and SortedList.cpp files compile just fine. They both also include .h files. I just do not understand why I get an error on that line. It seems to be a small issue though. Any insight would be appreciated. UPDATE1: I originally had .h files included, but i changed it when trying to figure out the cause of the error. The error remains with the .h files included though. UPDATE2: SortedList.h #ifndef SORTEDLIST_H #define SORTEDLIST_H #include "Student.h" /* * SortedList class * * A SortedList is an ordered collection of Students. The Students are ordered * from lowest numbered student ID to highest numbered student ID. */ class SortedList { public: SortedList(); // Constructs an empty list. SortedList(const SortedList & l); // Constructs a copy of the given student object ~SortedList(); // Destructs the sorted list object const SortedList & operator=(const SortedList & l); // Defines the assignment operator between two sorted list objects bool insert(Student *s); // If a student with the same ID is not already in the list, inserts // the given student into the list in the appropriate place and returns // true. If there is already a student in the list with the same ID // then the list is not changed and false is returned. Student *find(int studentID); // Searches the list for a student with the given student ID. If the // student is found, it is returned; if it is not found, NULL is returned. Student *remove(int studentID); // Searches the list for a student with the given student ID. If the // student is found, the student is removed from the list and returned; // if no student is found with the given ID, NULL is returned. // Note that the Student is NOT deleted - it is returned - however, // the removed list node should be deleted. void print() const; // Prints out the list of students to standard output. The students are // printed in order of student ID (from smallest to largest), one per line private: // Since Listnodes will only be used within the SortedList class, // we make it private. struct Listnode { Student *student; Listnode *next; }; Listnode *head; // pointer to first node in the list static void freeList(Listnode *L); // Traverses throught the linked list and deallocates each node static Listnode *copyList(Listnode *L); // Returns a pointer to the first node within a particular list }; #endif #ifndef STUDENT_H #define STUDENT_H Student.h #ifndef STUDENT_H #define STUDENT_H /* * Student class * * A Student object contains a student ID, the number of credits, and an * overall GPA. */ class Student { public: Student(); // Constructs a default student with an ID of 0, 0 credits, and 0.0 GPA. Student(int ID); // Constructs a student with the given ID, 0 credits, and 0.0 GPA. Student(int ID, int cr, double grPtAv); // Constructs a student with the given ID, number of credits, and GPA.\ Student(const Student & s); // Constructs a copy of another student object ~Student(); // Destructs a student object const Student & operator=(const Student & rhs); // Defines the assignment operator between two student objects // Accessors int getID() const; // returns the student ID int getCredits() const; // returns the number of credits double getGPA() const; // returns the GPA // Other methods void update(char grade, int cr); // Updates the total credits and overall GPA to take into account the // additions of the given letter grade in a course with the given number // of credits. The update is done by first converting the letter grade // into a numeric value (A = 4.0, B = 3.0, etc.). The new GPA is // calculated using the formula: // // (oldGPA * old_total_credits) + (numeric_grade * cr) // newGPA = --------------------------------------------------- // old_total_credits + cr // // Finally, the total credits is updated (to old_total_credits + cr) void print() const; // Prints out the student to standard output in the format: // ID,credits,GPA // Note: the end-of-line is NOT printed after the student information private: int studentID; int credits; double GPA; }; #endif

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• cut part of an image from an existing image in java

  - by Caylem

  Hi Currently working in Java, i'd like to be able to select part of an image using the mouse pointer co ordinates. The area selected then needs to be cut from the existing image and used to create a new separate image.

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• Skinning AIR application window

  - by Mike

  Hi, I'm using mx:WindowedApplication, I'm wondering how I can skin the title bar and close/minimize button for the window. I can see application like Pandora One is using it and setting transparency. Any pointer to a doc? Thanks,

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• C# Hide Resize Cursor

  - by Ozzy

  In my program, im using the WndProc override to stop my form being resized. Thing is, the cursor is still there when you move the pointer to the edge of the form. Is there anyway to hide this cursor?

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• Windows 7 SDK RC & Beta version

  - by Sarath

  Dear All, I've download Windows 7 SDK which was downloaded at the time of the beta release. Now I upgraded to RC and trying with some Direct2D samples. But I can't create the factory pointer using D2D1CreateFactory API. It's always returns NULL. Even the samples downloaded from MSDN is also not working well. There are some changes from Beta - RC Is this because of the version mismatch of SDK?

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• How to test a intellij plugin

  - by Journeyman Programmer

  Documentation on Intellij plugin development is scarce. If you have written any Intellij plugin, how did you write tests for plugin? Any pointer to documentation or source code is appreciated.

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• Difference between null==object and object==null

  - by priyank.mp

  Hi I would like to know diff between the above comparisons? I am getting null pointer exception when I check object.getItems() == null. But if I change it to null == object.getItems(), it workes fine. I did look into this http://stackoverflow.com/questions/2938476/what-is-the-difference-between-null-object-and-objectnull-closed But I didnt get satisfactory answer.

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• why weak_ptr can break cyclic reference?

  - by skydoor

  I learnt a lot about weak_ptr working with share_ptr to break cyclic reference. How does it work? How to use that? Can any body give me an example? I am totally lost here. One more question, what's a strong pointer?

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• Member variable pointers to COM objects

  - by drelihan

  Hi Folks, Is there any problem with keeping member variable pointer refernces to COM objects and reussing the reference through out the class in C++. Is anybody aware of a reason why you would want to call .CreateInstance every time you wanted a to use the COM object i.e. you were getting a fresh instance each time. I cannot see any reason who you would want to do this, Thanks, (No is an acceptable answer!!!)

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• How to declare NSString constants for passing to NSNotificationCenter

  - by synic

  I've got the following in my .h file: #ifndef _BALANCE_NOTIFICATION #define _BALANCE NOTIFICATION const NSString *BalanceUpdateNotification #endif and the following in my .m file: const NSString *BalanceUpdateNotification = @"BalanceUpdateNotification"; I'm using this with the following codes: [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(updateBalance:) name:BalanceUpdateNotification object:nil]; and [[NSNotificatoinCenter defaultCenter] postNotificationName:BalanceUpdateNotificatoin object:self userInfo:nil]; Which works, but it gives me a warning: Passing argument 1 of 'postNotificationName:object:userInfo' discards qualifiers from pointer target type So, I can cast it to (NSString *), but I'm wondering what the proper way to do this is.

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• ASP.Net HttpHandler ProcessRequest() firing twice

  - by Doug

  Hi there, I have a strange issue where i have a a HttpHandler having its ProcessRequest() event firing twice. i have nothing else in the class except a pointer to a static method so i'm lost. I have done some googling to no avail even thought it appears a few people are having similar issues: Code: public bool IsReusable { get { return true; } } public void ProcessRequest(HttpContext context) { Common.Tracker.TrackPageView(context); }

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• why are RTOS coded only in c?

  - by wrapperm

  Is it necessary to code RTOS in C language always? Why can't that be coded in java or some other technology..?? Is that because of the absence of pointer concept in java?

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• Changing code at runtime

  - by Pagis

  I have a pointer to a function (which i get from a vtable) and I want to edit the function by changing the assembler code (changing a few bytes) at runtime. I tried using memset and also tried assigning the new value directly (something like mPtr[0] = X, mPtr[1] = Y etc.) but I keep getting segmentation fault. How can I change the code? (I'm using C++)

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• Is "long" still useful in C?

  - by dan04

  It's not the largest integer type anymore now that there's "long long". It's not a fixed-width type: It's 32 bits on some platforms and 64 on others. It's not necessarily the same size as a pointer (for example, on 64-bit Windows) So, does "long" have any meaning anymore? Is there ever a reason to declare a long instead of a ptrdiff_t or int64_t?

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• How to attach to the jQuery Autocomplete plugin's mouse events?

  - by Tommy B

  My problem is this: I need to update some text in a div with the value of what the mouse pointer is hovering over in the autocomplete drop down list. Can it be done easily, or do I have to make fundamental changes to the Autocomplete plugin? I am using the jQuery Autocomplete plugin version 1.1 by Jörn Zaefferer. Any and all help will be greatly appreciated!

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• Hessian vs Tibco rv

  - by elec

  I'm looking to contrast Tibco rv and Hessian in terms of performance - for a Java application. Any pointer to get me started appreciated. thanks.

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• How to declare a(n) vector/array of reducer objects in Cilk++?

  - by Jin

  Hi All, I had a problem when I am using Cilk++, an extension to C++ for parallel computing. I found that I can't declare a vector of reducer objects: typedef cilk::reducer_opadd<int> T_reducer; vector<T_reducer> bitmiss_vec; for (int i = 0; i < 24; ++i) { T_reducer r; bitmiss_vec.push_back(r); } However, when I compile the code with Cilk++, it complains at the push_back() line: cilk++ geneAttack.cilk -O1 -g -lcilkutil -o geneAttack /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h: In member function ‘void __gnu_cxx::new_allocator<_Tp>::construct(_Tp*, const _Tp&) [with _Tp = cilk::reducer_opadd<int>]’: /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_vector.h:601: instantiated from ‘void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ geneAttack.cilk:667: instantiated from here /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h:229: error: ‘cilk::reducer_opadd<Type>::reducer_opadd(const cilk::reducer_opadd<Type>&) [with Type = int]’ is private /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/ext/new_allocator.h:107: error: within this context /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h: In member function ‘void std::vector<_Tp, _Alloc>::_M_insert_aux(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’: /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_vector.h:605: instantiated from ‘void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ geneAttack.cilk:667: instantiated from here /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h:229: error: ‘cilk::reducer_opadd<Type>::reducer_opadd(const cilk::reducer_opadd<Type>&) [with Type = int]’ is private /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/vector.tcc:252: error: within this context /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_vector.h:605: instantiated from ‘void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ geneAttack.cilk:667: instantiated from here /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h:230: error: ‘cilk::reducer_opadd<Type>& cilk::reducer_opadd<Type>::operator=(const cilk::reducer_opadd<Type>&) [with Type = int]’ is private /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/vector.tcc:256: error: within this context /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h: In static member function ‘static _BI2 std::__copy_backward<_BoolType, std::random_access_iterator_tag>::__copy_b(_BI1, _BI1, _BI2) [with _BI1 = cilk::reducer_opadd<int>*, _BI2 = cilk::reducer_opadd<int>*, bool _BoolType = false]’: /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_algobase.h:465: instantiated from ‘_BI2 std::__copy_backward_aux(_BI1, _BI1, _BI2) [with _BI1 = cilk::reducer_opadd<int>*, _BI2 = cilk::reducer_opadd<int>*]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_algobase.h:474: instantiated from ‘static _BI2 std::__copy_backward_normal<<anonymous>, <anonymous> >::__copy_b_n(_BI1, _BI1, _BI2) [with _BI1 = cilk::reducer_opadd<int>*, _BI2 = cilk::reducer_opadd<int>*, bool <anonymous> = false, bool <anonymous> = false]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_algobase.h:540: instantiated from ‘_BI2 std::copy_backward(_BI1, _BI1, _BI2) [with _BI1 = cilk::reducer_opadd<int>*, _BI2 = cilk::reducer_opadd<int>*]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/vector.tcc:253: instantiated from ‘void std::vector<_Tp, _Alloc>::_M_insert_aux(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_vector.h:605: instantiated from ‘void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ geneAttack.cilk:667: instantiated from here /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h:230: error: ‘cilk::reducer_opadd<Type>& cilk::reducer_opadd<Type>::operator=(const cilk::reducer_opadd<Type>&) [with Type = int]’ is private /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_algobase.h:433: error: within this context /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h: In function ‘void std::_Construct(_T1*, const _T2&) [with _T1 = cilk::reducer_opadd<int>, _T2 = cilk::reducer_opadd<int>]’: /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_uninitialized.h:87: instantiated from ‘_ForwardIterator std::__uninitialized_copy_aux(_InputIterator, _InputIterator, _ForwardIterator, std::__false_type) [with _InputIterator = cilk::reducer_opadd<int>*, _ForwardIterator = cilk::reducer_opadd<int>*]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_uninitialized.h:114: instantiated from ‘_ForwardIterator std::uninitialized_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = cilk::reducer_opadd<int>*, _ForwardIterator = cilk::reducer_opadd<int>*]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_uninitialized.h:254: instantiated from ‘_ForwardIterator std::__uninitialized_copy_a(_InputIterator, _InputIterator, _ForwardIterator, std::allocator<_Tp>) [with _InputIterator = cilk::reducer_opadd<int>*, _ForwardIterator = cilk::reducer_opadd<int>*, _Tp = cilk::reducer_opadd<int>]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/vector.tcc:275: instantiated from ‘void std::vector<_Tp, _Alloc>::_M_insert_aux(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_vector.h:605: instantiated from ‘void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ geneAttack.cilk:667: instantiated from here /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h:229: error: ‘cilk::reducer_opadd<Type>::reducer_opadd(const cilk::reducer_opadd<Type>&) [with Type = int]’ is private /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_construct.h:81: error: within this context make: *** [geneAttack] Error 1 jinchen@galactica:~/workspace/biometrics/genAttack$ make cilk++ geneAttack.cilk -O1 -g -lcilkutil -o geneAttack geneAttack.cilk: In function ‘int cilk cilk_main(int, char**)’: geneAttack.cilk:670: error: expected primary-expression before ‘,’ token geneAttack.cilk:670: error: expected primary-expression before ‘}’ token geneAttack.cilk:674: error: ‘bitmiss_vec’ was not declared in this scope make: *** [geneAttack] Error 1 The Cilk++ manule says it supports array/vector of reducers, although there are performance issues to consider: "If you create a large number of reducers (for example, an array or vector of reducers) you must be aware that there is an overhead at steal and reduce that is proportional to the number of reducers in the program. " Anyone knows what is going on? How should I declare/use vector of reducers? Thank you

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• Java mouse motion anywhere on screen

  - by Dave

  I'm sure this is possible but all my searching is coming up blank. In Java is it possible to register for a mouse motion event outside of a Java app? So if the mouse pointer moves anywhere on the screen I get a call back. An approximation is possible with polling MouseInfo.getPointerInfo but there must be a better way. Thanks

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• Function lfit in numerical recipes, providing a test function

  - by Simon Walker

  Hi I am trying to fit collected data to a polynomial equation and I found the lfit function from Numerical Recipes. I only have access to the second edition, so am using that. I have read about the lfit function and its parameters, one of which is a function pointer, given in the documentation as void (*funcs)(float, float [], int)) with the help The user supplies a routine funcs(x,afunc,ma) that returns the ma basis functions evaluated at x = x in the array afunc[1..ma]. I am struggling to understand how this lfit function works. An example function I found is given below: void fpoly(float x, float p[], int np) /*Fitting routine for a polynomial of degree np-1, with coe?cients in the array p[1..np].*/ { int j; p[1]=1.0; for (j=2;j<=np;j++) p[j]=p[j-1]*x; } When I run through the source code for the lfit function in gdb I can see no reference to the funcs pointer. When I try and fit a simple data set with the function, I get the following error message. Numerical Recipes run-time error... gaussj: Singular Matrix ...now exiting to system... Clearly somehow a matrix is getting defined with all zeroes. I am going to involve this function fitting in a large loop so using another language is not really an option. Hence why I am planning on using C/C++. For reference, the test program is given here: int main() { float x[5] = {0., 0., 1., 2., 3.}; float y[5] = {0., 0., 1.2, 3.9, 7.5}; float sig[5] = {1., 1., 1., 1., 1.}; int ndat = 4; int ma = 4; /* parameters in equation */ float a[5] = {1, 1, 1, 0.1, 1.5}; int ia[5] = {1, 1, 1, 1, 1}; float **covar = matrix(1, ma, 1, ma); float chisq = 0; lfit(x,y,sig,ndat,a,ia,ma,covar,&chisq,fpoly); printf("%f\n", chisq); free_matrix(covar, 1, ma, 1, ma); return 0; } Also confusing the issue, all the Numerical Recipes functions are 1 array-indexed so if anyone has corrections to my array declarations let me know also! Cheers

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• How to use mmap to point to STL type?

  - by srikfreak

  I have a mmap typecast to a char pointer char *ptr; ptr = (char *)mmap(0, FILESIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); This was my earlier code. But now I want to use a map instead of char * as the requirements changed. Now, my map is declared as map i_s_map; How do I change my mmap call to point to the map?

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• To capture Tv tuner output

  - by mawia

  Hi! all, We are developting a tool for live video streaming in which we want to broadcast the output of tv tuner on a network.Our project is at it's nascent stage.Our main concern at this moment is to how to capture the output of a tv tuner card.Plz guide us regarding this or provide a pointer where I can detail about the topic. All help will be highly appreciated. Thanks Mawia

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• Marshalling to a native library in C#

  - by Daniel Baulig

  I'm having trouble calling functions of a native library from within managed C# code. I am developing for the 3.5 compact framework (Windows Mobile 6.x) just in case this would make any difference. I am working with the waveIn* functions from coredll.dll (these are in winmm.dll in regular Windows I believe). This is what I came up with: // namespace winmm; class winmm [StructLayout(LayoutKind.Sequential)] public struct WAVEFORMAT { public ushort wFormatTag; public ushort nChannels; public uint nSamplesPerSec; public uint nAvgBytesPerSec; public ushort nBlockAlign; public ushort wBitsPerSample; public ushort cbSize; } [StructLayout(LayoutKind.Sequential)] public struct WAVEHDR { public IntPtr lpData; public uint dwBufferLength; public uint dwBytesRecorded; public IntPtr dwUser; public uint dwFlags; public uint dwLoops; public IntPtr lpNext; public IntPtr reserved; } public delegate void AudioRecordingDelegate(IntPtr deviceHandle, uint message, IntPtr instance, ref WAVEHDR wavehdr, IntPtr reserved2); [DllImport("coredll.dll")] public static extern int waveInAddBuffer(IntPtr hWaveIn, ref WAVEHDR lpWaveHdr, uint cWaveHdrSize); [DllImport("coredll.dll")] public static extern int waveInPrepareHeader(IntPtr hWaveIn, ref WAVEHDR lpWaveHdr, uint Size); [DllImport("coredll.dll")] public static extern int waveInStart(IntPtr hWaveIn); // some other class private WinMM.WinMM.AudioRecordingDelegate waveIn; private IntPtr handle; private uint bufferLength; private void setupBuffer() { byte[] buffer = new byte[bufferLength]; GCHandle bufferPin = GCHandle.Alloc(buffer, GCHandleType.Pinned); WinMM.WinMM.WAVEHDR hdr = new WinMM.WinMM.WAVEHDR(); hdr.lpData = bufferPin.AddrOfPinnedObject(); hdr.dwBufferLength = this.bufferLength; hdr.dwFlags = 0; int i = WinMM.WinMM.waveInPrepareHeader(this.handle, ref hdr, Convert.ToUInt32(Marshal.SizeOf(hdr))); if (i != WinMM.WinMM.MMSYSERR_NOERROR) { this.Text = "Error: waveInPrepare"; return; } i = WinMM.WinMM.waveInAddBuffer(this.handle, ref hdr, Convert.ToUInt32(Marshal.SizeOf(hdr))); if (i != WinMM.WinMM.MMSYSERR_NOERROR) { this.Text = "Error: waveInAddrBuffer"; return; } } private void setupWaveIn() { WinMM.WinMM.WAVEFORMAT format = new WinMM.WinMM.WAVEFORMAT(); format.wFormatTag = WinMM.WinMM.WAVE_FORMAT_PCM; format.nChannels = 1; format.nSamplesPerSec = 8000; format.wBitsPerSample = 8; format.nBlockAlign = Convert.ToUInt16(format.nChannels * format.wBitsPerSample); format.nAvgBytesPerSec = format.nSamplesPerSec * format.nBlockAlign; this.bufferLength = format.nAvgBytesPerSec; format.cbSize = 0; int i = WinMM.WinMM.waveInOpen(out this.handle, WinMM.WinMM.WAVE_MAPPER, ref format, Marshal.GetFunctionPointerForDelegate(waveIn), 0, WinMM.WinMM.CALLBACK_FUNCTION); if (i != WinMM.WinMM.MMSYSERR_NOERROR) { this.Text = "Error: waveInOpen"; return; } setupBuffer(); WinMM.WinMM.waveInStart(this.handle); } I read alot about marshalling the last few days, nevertheless I do not get this code working. When my callback function is called (waveIn) when the buffer is full, the hdr structure passed back in wavehdr is obviously corrupted. Here is an examlpe of how the structure looks like at that point: - wavehdr {WinMM.WinMM.WAVEHDR} WinMM.WinMM.WAVEHDR dwBufferLength 0x19904c00 uint dwBytesRecorded 0x0000fa00 uint dwFlags 0x00000003 uint dwLoops 0x1990f6a4 uint + dwUser 0x00000000 System.IntPtr + lpData 0x00000000 System.IntPtr + lpNext 0x00000000 System.IntPtr + reserved 0x7c07c9a0 System.IntPtr This obiously is not what I expected to get passed. I am clearly concerned about the order of the fields in the view. I do not know if Visual Studio .NET cares about actual memory order when displaying the record in the "local"-view, but they are obviously not displayed in the order I speciefied in the struct. Then theres no data pointer and the bufferLength field is far to high. Interestingly the bytesRecorded field is exactly 64000 - bufferLength and bytesRecorded I'd expect both to be 64000 though. I do not know what exactly is going wrong, maybe someone can help me out on this. I'm an absolute noob to managed code programming and marshalling so please don't be too harsh to me for all the stupid things I've propably done. Oh here's the C code definition for WAVEHDR which I found here, I believe I might have done something wrong in the C# struct definition: /* wave data block header */ typedef struct wavehdr_tag { LPSTR lpData; /* pointer to locked data buffer */ DWORD dwBufferLength; /* length of data buffer */ DWORD dwBytesRecorded; /* used for input only */ DWORD_PTR dwUser; /* for client's use */ DWORD dwFlags; /* assorted flags (see defines) */ DWORD dwLoops; /* loop control counter */ struct wavehdr_tag FAR *lpNext; /* reserved for driver */ DWORD_PTR reserved; /* reserved for driver */ } WAVEHDR, *PWAVEHDR, NEAR *NPWAVEHDR, FAR *LPWAVEHDR; If you are used to work with all those low level tools like pointer-arithmetic, casts, etc starting writing managed code is a pain in the ass. It's like trying to learn how to swim with your hands tied on your back. Some things I tried (to no effect): .NET compact framework does not seem to support the Pack = 2^x directive in [StructLayout]. I tried [StructLayout(LayoutKind.Explicit)] and used 4 bytes and 8 bytes alignment. 4 bytes alignmentgave me the same result as the above code and 8 bytes alignment only made things worse - but that's what I expected. Interestingly if I move the code from setupBuffer into the setupWaveIn and do not declare the GCHandle in the context of the class but in a local context of setupWaveIn the struct returned by the callback function does not seem to be corrupted. I am not sure however why this is the case and how I can use this knowledge to fix my code. I'd really appreciate any good links on marshalling, calling unmanaged code from C#, etc. Then I'd be very happy if someone could point out my mistakes. What am I doing wrong? Why do I not get what I'd expect.

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• A couple questions using fwrite/fread with data structures

  - by Nazgulled

  Hi, I'm using fwrite() and fread() for the first time to write some data structures to disk and I have a couple of questions about best practices and proper ways of doing things. What I'm writing to disk (so I can later read it back) is all user profiles inserted in a Graph structure. Each graph vertex is of the following type: typedef struct sUserProfile { char name[NAME_SZ]; char address[ADDRESS_SZ]; int socialNumber; char password[PASSWORD_SZ]; HashTable *mailbox; short msgCount; } UserProfile; And this is how I'm currently writing all the profiles to disk: void ioWriteNetworkState(SocialNetwork *social) { Vertex *currPtr = social->usersNetwork->vertices; UserProfile *user; FILE *fp = fopen("save/profiles.dat", "w"); if(!fp) { perror("fopen"); exit(EXIT_FAILURE); } fwrite(&(social->usersCount), sizeof(int), 1, fp); while(currPtr) { user = (UserProfile*)currPtr->value; fwrite(&(user->socialNumber), sizeof(int), 1, fp); fwrite(user->name, sizeof(char)*strlen(user->name), 1, fp); fwrite(user->address, sizeof(char)*strlen(user->address), 1, fp); fwrite(user->password, sizeof(char)*strlen(user->password), 1, fp); fwrite(&(user->msgCount), sizeof(short), 1, fp); break; currPtr = currPtr->next; } fclose(fp); } Notes: The first fwrite() you see will write the total user count in the graph so I know how much data I need to read back. The break is there for testing purposes. There's thousands of users and I'm still experimenting with the code. My questions: After reading this I decided to use fwrite() on each element instead of writing the whole structure. I also avoid writing the pointer to to the mailbox as I don't need to save that pointer. So, is this the way to go? Multiple fwrite()'s instead of a global one for the whole structure? Isn't that slower? How do I read back this content? I know I have to use fread() but I don't know the size of the strings, cause I used strlen() to write them. I could write the output of strlen() before writing the string, but is there any better way without extra writes?

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• Is there any reasonable use of a function returning an anonymous struct?

  - by Akanksh

  Here is an (artificial) example of using a function that returns an anonymous struct and does "something" useful: #include <iostream> template<typename T> T* func( T* t, float a, float b ) { if(!t) { t = new T; t->a = a; t->b = b; } else { t->a += a; t->b += b; } return t; } struct { float a, b; }* foo(float a, float b) { if(a==0) return 0; return func(foo(a-1,b), a, b); } int main() { std::cout << foo(5,6)->a << std::endl; std::cout << foo(5,6)->b << std::endl; void* v = (void*)(foo(5,6)); float* f = (float*)(v); //[1] delete f now because I know struct is floats only. std::cout << f[0] << std::endl; std::cout << f[1] << std::endl; delete[] f; return 0; } There are a few points I would like to discuss: As is apparent, this code leaks, is there anyway I can NOT leak without knowing what the underlying struct definition is? see Comment [1]. I have to return a pointer to an anonymous struct so I can create an instance of the object within the templatized function func, can I do something similar without returning a pointer? I guess the most important, is there ANY (real-world) use for this at all? As the example given above leaks and is admittedly contrived. By the way, what the function foo(a,b) does is, to return a struct containing two numbers, the sum of all numbers from 1 to a and the product of a and b. EDIT: Maybe the line new T could use a boost::shared_ptr somehow to avoid leaks, but I haven't tried that. Would that work?

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