March 2011 - Boost-users - lists.preview.boost.org

Re: [Boost-users] Thread Interruption Best Practice
by Dom Driver 24 Mar '11

24 Mar '11

> if I understand your problem you want the thread blocking in select to return? Correct. I need this call to return when: 1) I've got some data waiting to be read. 2) The application is terminating and I want to stop my RX communications thread. The first one is straightforward. I'll investigate the use of pipes as a secondary option. As for 2), from other suggestions, I've gone back to the ASIO library. I read about slushies and brain-freeze, and thought it might be the way to go. However, I think I've managed to fall victim to brainfreeze myself. >From the ASIO example at: http://www.boost.org/doc/libs/1_46_1/doc/html/boost_asio/example/echo/async… This is an asynchronous server similar to what I'm trying to do here. I've got a couple of questions on this, 1) When the server object is created, the call to socket.async_read_from() is made immediately. If there is no data waiting, to be read, this call returns immediately, right? 2) When data does arrive, the handler 'handle_receive_from()' is called. Regardless of whether some bytes are read or not, we eventually call socket.async_read_from() again. This is probably quite fundamental to what I'm misunderstanding, but doesn't this mean I'll be effectively calling socket.async_read_from() from within the handler of a call to socket.async_read_from()? Will I be recursing indefinitely until the application terminates? That doesn't sound right, so I must be missing something very obvious here. Hmmm. Biblical-style ray-of-light guidance appreciated!

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Project using Boost won't build with Xcode 4; complains about "global weak symbols"
by G S 23 Mar '11

23 Mar '11

Hi all. I'm using Boost in an iPhone app as a statically linked lib, and after updating to Xcode 4 the project won't build. It fails with this: *ld: bad codegen, pointer diff in boost::system::error_category:* *:error_category()to global weak symbol vtable for boost::system::error_**categoryfor architecture i386* Happens for both simulator and device, after the same project built fine under previous Xcodes. Anybody have some insight on this and a solution? Thanks! Gavin

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[uBLAS] Matrix creation vs resize
by Ryan 23 Mar '11

23 Mar '11

I need to remove rows from a matrix if it fails a comparison. I have two possible options to remove the matrix rows. Option 1 adds a row to the new matrix for each row from the old matrix that passes the comparison. Option 2 keeps track of the rows from the old matrix that passed the comparison and then creates a new matrix all at once. I'm wondering which option is more efficient or is there a simpler way to achieve the same results? Ryan Option 1 void( matrix<double> const& H, matrix<double> const& P, matrix<double> const& R, vector<double> const& v) { double const rejection_criterion = 2; matrix<double> M = prod(H, matrix<double>(prod(P, trans(H))) + R; matrix<double> result; int matrix_size = 1; for (unsigned i = 0; i < v.size(); ++i) { if ( v[i] * v[i] < rejection_criterion * M(i,i)) { result.resize(matrix_size, H.size2(), true); matrix_row<matrix<double> > oldH (H, i); matrix_row<matrix<double> > newH (result, matrix_size - 1); newH = oldH; matrix_size++; } } } Option 2 void( matrix<double> const& H, matrix<double> const& P, matrix<double> const& R, vector<double> const& v) { double const rejection_criterion = 2; matrix<double> M = prod(H, matrix<double>(prod(P, trans(H))) + R; list<unsigned> goodrows; for (unsigned i = 0; i < v.size(); ++i) { if ( v[i] * v[i] < rejection_criterion * M(i,i)) { goodrows.push_back(i); } } matrix<double> result(goodrows.size(), H.size2()); for ( unsigned i = 0, list<unsigned>::iterator iter = goodrows.begin(); i < result.size1(); ++i, ++iter) { matrix_row<matrix<double> > oldH (H, *iter); matrix_row<matrix<double> > newH (result, i); newH = oldH; } }

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String transformation using string_algo
by Remko Tronçon 23 Mar '11

23 Mar '11

Hi, I want to apply an (un-)escaping transformation on a string (e.g., map "<" to "<", map ">" to "<", ...). I was wondering whether boost string algorithms can provide a good way of doing this or not. I was corsidering find_format, but the problem there is that the finder has to check for occurrence of "<" (by matching a string), but then the formatter needs to check again which of the strings the finder matched ("<", ">") to emit the correct character, which sounds suboptimal. A workaround would be to make the finder always succeed, and let the formatter do the actual check and emit the string if it matches. Is there a better alternative? I also noticed there's a "transform_range_copy", but this isn't documented. thanks! Remko

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any __cxa_demangle / UnDecorateSymbolName in boost ?
by Vial, Florent 23 Mar '11

23 Mar '11

Hi all, i want to retrieve the class name of some std::type_info in my application. is there any function to help me with this within boost ? I looked for it in the boost 1.46.1 code but did not find anything. My problem is that UnDecorateSymbolName is not thread safe under Windows. Thank you in advance, Florent ________________________________ Arnold & Richter Cine Technik GmbH & Co. Betriebs KG Sitz: München - Registergericht: Amtsgericht München - Handelsregisternummer: HRA 57918 Persönlich haftender Gesellschafter: Arnold & Richter Cine Technik GmbH Sitz: München - Registergericht: Amtsgericht München - Handelsregisternummer: HRB 54477 Geschäftsführer: Franz Kraus; Dr. Martin Prillmann [http://www.arri.de/fileadmin/mail_images/CTBanner.gif] A new star is born – ALEXA the most versatile digital camera system. Get all the latest information from arridigital.com and YouTube.

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Traversing a graph
by Vipin Varma 23 Mar '11

23 Mar '11

Hi, I have a quick question about graph traversal: what is the appropriate algorithm to be used if I want to find the shortest distance between 2 specified vertices {v_s, v_d} such that every edge on the graph is traversed at least once? I've already used the breadth_first_search() and dijkstras_shortest_paths() for other problems wherein v_s = v_d. Seemingly, these algorithms cannot be used when the source and destination vertices are dissimilar. Thanks, Vipin

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serialization example
by Marco Piacentini 23 Mar '11

23 Mar '11

Hi guys..a very simple question... In the example of the serialization, before serialize, an header is linked to the data. It will be handle both in write and read operations. Is this header essential for the serialization process, or it can be omitted and I can serialize only the data? thank you...

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issues when using boost.bind from boost.thread
by Sean Farrow 23 Mar '11

23 Mar '11

Hi: I'm trying to use boost.bind when starting a thread. The following code starts a thread and tries to pass in a boost.asio.io_service as well. boost::thread* t = new boost::thread(boost::bind(&boost::asio::io_service::run, &io)); I'm getting the following exception when running this code. Unhandled exception at 0x7c812afb in MDRLite.exe: Microsoft C++ exception: boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::system::system_error> > Removing the previous block of code removes the error. Having read the boost.bind, The boost.tread/boost.asio documentation I carn't seem to find what is wrong. This seems to be the final piece of the jigsaw that I carn't seem to crack! Any help appreciated. Cheers Sean.

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[Statechart] Why does this state machine enter unstable state only in debug mode?
by Zhu Bicen 23 Mar '11

23 Mar '11

I am trying to use statechart in a player application. And found a weird issue, so I write following code to reproduce the issue and ask for help. 1. call the MciWndPlay win32API to play a music file within a state entry action 2. Windows msg , which indicate the player current player position, is coming 3. call process_event within Windows procedure 4. but assert failed: get_pointer(pOutermostUnstableState_) == 0 It seems the PlayingState entry action does not execute completely, The debug message after MciWndPlay call is not also printed out, but another event is coming, But This is a single thread application, the MciWndPlay is just Send Message to something and return immediately. I also print out the thread ID, all is the same. Another thing is this assert failure is only occurred in Debug Mode, in release mode all goes well. I am using Visual C++ 2008 express, and boost 1.46.1. Any comments and indication is welcome. I am confused by this issue several days. Thanks in advance. // BugFix.cpp : Defines the entry point for the application. // #include "stdafx.h" #include "BugFix.h" #include "Vfw.h" #include <iostream> #include <boost/statechart/event.hpp> #include <boost/statechart/state_machine.hpp> #include <boost/statechart/simple_state.hpp> #include <boost/statechart/state.hpp> #include <boost/statechart/custom_reaction.hpp> #include <boost/statechart/transition.hpp> #include <boost/statechart/result.hpp> #include <mmsystem.h> #pragma comment(lib, "vfw32.lib") namespace fsm = boost::statechart; #define MAX_LOADSTRING 100 // Global Variables: HINSTANCE hInst; TCHAR szTitle[MAX_LOADSTRING]; TCHAR szWindowClass[MAX_LOADSTRING]; std::wstring file_name = L"D:\\VOA\\5. Deep Six It Is Well Hidden.mp3"; // Forward declarations of functions included in this code module: ATOM MyRegisterClass(HINSTANCE hInstance); BOOL InitInstance(HINSTANCE, int); LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM); INT_PTR CALLBACK About(HWND, UINT, WPARAM, LPARAM); static std::wstring FILE_NAME = L""; struct OpenFileEvent: public fsm::event< OpenFileEvent >{ std::wstring file_name; OpenFileEvent(const std::wstring p_file_name):file_name(p_file_name){} }; struct UpdatePosEvent: public fsm::event< UpdatePosEvent >{ long pos; UpdatePosEvent(long position): pos(position){} }; class WaitingForFileState; class PlayingState; class PlayerFsm : public fsm::state_machine< PlayerFsm, WaitingForFileState > { public: friend class WaitingForFileState; friend class HandlingFileState; friend class PlayingState; }; class WaitingForFileState: public fsm::simple_state< WaitingForFileState, PlayerFsm > { public: typedef fsm::custom_reaction< OpenFileEvent > reactions; fsm::result react( const OpenFileEvent& evt) { std::cout << "OpenFileEvent is received " << std::endl; FILE_NAME = evt.file_name; return transit< HandlingFileState >(); } }; class HandlingFileState: public fsm::state< HandlingFileState, PlayerFsm, PlayingState> { public: HandlingFileState( my_context ctx ): my_base( ctx){ MCIWndOpen(_playerWnd, FILE_NAME.c_str(), NULL); } }; class PlayingState: public fsm::simple_state< PlayingState, HandlingFileState> { public: PlayingState() { std::cout << "Entering PlayingState" << std::endl; std::cout << "fsm threadId = " << GetCurrentThreadId() << std::endl; assert(MCIWndPlay(_playerWnd) == 0); // below message is not printed out in debug mode, // and another message UpdatePosEvent come // and StateChart assert failure std::cout << "After MCIWndPlay" << std::endl; } typedef fsm::custom_reaction< UpdatePosEvent > reactions; fsm::result react( const UpdatePosEvent& evt){ std::cout << "UpdatePosEvent is received in PlayingState" << std::endl; return fsm::detail::result_utility:: make_result( fsm::detail::consumed ); } private: long current_pos_; }; HWND _playerWnd; PlayerFsm _player_fsm; int APIENTRY _tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow) { AllocConsole(); freopen("CONOUT$", "w+t", stdout); freopen("CONOUT$", "w+t", stderr); std::cout << "threadId = " << GetCurrentThreadId() << std::endl; UNREFERENCED_PARAMETER(hPrevInstance); UNREFERENCED_PARAMETER(lpCmdLine); // TODO: Place code here. MSG msg; HACCEL hAccelTable; // Initialize global strings LoadString(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING); LoadString(hInstance, IDC_BUGFIX, szWindowClass, MAX_LOADSTRING); MyRegisterClass(hInstance); // Perform application initialization: if (!InitInstance (hInstance, nCmdShow)) { return FALSE; } hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_BUGFIX)); // Main message loop: while (GetMessage(&msg, NULL, 0, 0)) { if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg)) { TranslateMessage(&msg); DispatchMessage(&msg); } } return (int) msg.wParam; } ATOM MyRegisterClass(HINSTANCE hInstance) { WNDCLASSEX wcex; wcex.cbSize = sizeof(WNDCLASSEX); wcex.style = CS_HREDRAW | CS_VREDRAW; wcex.lpfnWndProc = WndProc; wcex.cbClsExtra = 0; wcex.cbWndExtra = 0; wcex.hInstance = hInstance; wcex.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_BUGFIX)); wcex.hCursor = LoadCursor(NULL, IDC_ARROW); wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1); wcex.lpszMenuName = MAKEINTRESOURCE(IDC_BUGFIX); wcex.lpszClassName = szWindowClass; wcex.hIconSm = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL)); return RegisterClassEx(&wcex); } BOOL InitInstance(HINSTANCE hInstance, int nCmdShow) { HWND hWnd; hInst = hInstance; // Store instance handle in our global variable hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL); if (!hWnd) { return FALSE; } ShowWindow(hWnd, nCmdShow); UpdateWindow(hWnd); return TRUE; } LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) { int wmId, wmEvent; PAINTSTRUCT ps; HDC hdc; switch (message) { case WM_COMMAND: wmId = LOWORD(wParam); wmEvent = HIWORD(wParam); // Parse the menu selections: switch (wmId) { case IDM_ABOUT: _player_fsm.process_event(OpenFileEvent(file_name)); //DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About); break; case IDM_EXIT: DestroyWindow(hWnd); break; default: return DefWindowProc(hWnd, message, wParam, lParam); } break; case WM_CREATE: _player_fsm.initiate(); _playerWnd = MCIWndCreate( hWnd, hInst, MCIWNDF_NOTIFYPOS|MCIWNDF_NOMENU|MCIWNDF_NOTIFYMODE, NULL); break; case MCIWNDM_NOTIFYPOS: std::cout << "received MCIWNDM_NOTIFYPOS msg, threadId = " << GetCurrentThreadId() << std::endl; _player_fsm.process_event(UpdatePosEvent(lParam)); break; case WM_PAINT: hdc = BeginPaint(hWnd, &ps); EndPaint(hWnd, &ps); break; case WM_DESTROY: PostQuitMessage(0); break; default: return DefWindowProc(hWnd, message, wParam, lParam); } return 0; } -- Best Regards Bicen Zhu

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Boost.Test: test suite with parameter
by Hendrik Fuß 23 Mar '11

23 Mar '11

Hi folks, I've got a suite of tests that test the functions of an abstraction layer. What I would like to do is to apply this suite to any number of concrete implementations of the abstract interface. That is, my test suite should have one parameter, say, a pointer to the abstract interface's implementation. I know I can register unary function based test cases, but how can I provide an argument to an entire test suite? I wasn't able to figure this out. Appreciate any help. cheers Hendrik

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