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  • boost::asio::async_read_until problem

    - by user368831
    Hi again, I'm modify the boost asio echo example to use async_read_until to read the input word by word. Even though I am using async_read_until all the data sent seems to be read from the socket. Could someone please advise: #include <cstdlib> #include <iostream> #include <boost/bind.hpp> #include <boost/asio.hpp> using boost::asio::ip::tcp; class session { public: session(boost::asio::io_service& io_service) : socket_(io_service) { } tcp::socket& socket() { return socket_; } void start() { std::cout<<"starting"<<std::endl; boost::asio::async_read_until(socket_, buffer, ' ', boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } void handle_read(const boost::system::error_code& error, size_t bytes_transferred) { std::ostringstream ss; ss<<&buffer; std::string s = ss.str(); std::cout<<s<<std::endl; if (!error) { boost::asio::async_write(socket_, boost::asio::buffer(s), boost::bind(&session::handle_write, this, boost::asio::placeholders::error)); } else { delete this; } } void handle_write(const boost::system::error_code& error) { std::cout<<"handling write"<<std::endl; if (!error) { } else { delete this; } } private: tcp::socket socket_; boost::asio::streambuf buffer; }; class server { public: server(boost::asio::io_service& io_service, short port) : io_service_(io_service), acceptor_(io_service, tcp::endpoint(tcp::v4(), port)) { session* new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } void handle_accept(session* new_session, const boost::system::error_code& error) { if (!error) { new_session->start(); new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } else { delete new_session; } } private: boost::asio::io_service& io_service_; tcp::acceptor acceptor_; }; int main(int argc, char* argv[]) { try { if (argc != 2) { std::cerr << "Usage: async_tcp_echo_server <port>\n"; return 1; } boost::asio::io_service io_service; using namespace std; // For atoi. server s(io_service, atoi(argv[1])); io_service.run(); } catch (std::exception& e) { std::cerr << "Exception: " << e.what() << "\n"; } return 0; } Thanks!

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  • Is Programming == Math?

    - by moffdub
    I've heard many times that all programming is really a subset of math. Some suggest that OO, at its roots, is mathematically based. I don't get the connection. Aside from some obvious examples: using induction to prove a recursive algorithm formal correctness proofs functional languages lambda calculus asymptotic complexity DFAs, NFAs, Turing Machines, and theoretical computation in general the fact that everything on the box is binary In what ways is programming really a subset of math? I'm looking for an explanation that might have relevance to enterprise/OO development (if there is a strong enough connection, that is). Thanks in advance. Edit: as I stated in a comment to an answer, math is uber important to programming, but what I struggle with is the "subset" argument.

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  • Need Help Setting an Image with Transparent Background to Clipboard

    - by AMissico
    I need help setting a transparent image to the clipboard. I keep getting "handle is invalid". Basically, I need a "second set of eyes" to look over the following code. (The complete working project at ftp://missico.net/ImageVisualizer.zip.) This is an image Debug Visualizer class library, but I made the included project to run as an executable for testing. (Note that window is a toolbox window and show in taskbar is set to false.) I was tired of having to perform a screen capture on the toolbox window, open the screen capture with an image editor, and then deleting the background added because it was a screen capture. So I thought I would quickly put the transparent image onto the clipboard. Well, the problem is...no transparency support for Clipboard.SetImage. Google to the rescue...not quite. This is what I have so far. I pulled from a number of sources. See the code for the main reference. My problem is the "invalid handle" when using CF_DIBV5. Do I need to use BITMAPV5HEADER and CreateDIBitmap? Any help from you GDI/GDI+ Wizards would be greatly appreciated. public static void SetClipboardData(Bitmap bitmap, IntPtr hDC) { const uint SRCCOPY = 0x00CC0020; const int CF_DIBV5 = 17; const int CF_BITMAP = 2; //'reference //'http://social.msdn.microsoft.com/Forums/en-US/winforms/thread/816a35f6-9530-442b-9647-e856602cc0e2 IntPtr memDC = CreateCompatibleDC(hDC); IntPtr memBM = CreateCompatibleBitmap(hDC, bitmap.Width, bitmap.Height); SelectObject(memDC, memBM); using (Graphics g = Graphics.FromImage(bitmap)) { IntPtr hBitmapDC = g.GetHdc(); IntPtr hBitmap = bitmap.GetHbitmap(); SelectObject(hBitmapDC, hBitmap); BitBlt(memDC, 0, 0, bitmap.Width, bitmap.Height, hBitmapDC, 0, 0, SRCCOPY); if (!OpenClipboard(IntPtr.Zero)) { throw new System.Runtime.InteropServices.ExternalException("Could not open Clipboard", new Win32Exception()); } if (!EmptyClipboard()) { throw new System.Runtime.InteropServices.ExternalException("Unable to empty Clipboard", new Win32Exception()); } //IntPtr hClipboard = SetClipboardData(CF_BITMAP, memBM); //works but image is not transparent //all my attempts result in SetClipboardData returning hClipboard = IntPtr.Zero IntPtr hClipboard = SetClipboardData(CF_DIBV5, memBM); //because if (hClipboard == IntPtr.Zero) { // InnerException: System.ComponentModel.Win32Exception // Message="The handle is invalid" // ErrorCode=-2147467259 // NativeErrorCode=6 // InnerException: throw new System.Runtime.InteropServices.ExternalException("Could not put data on Clipboard", new Win32Exception()); } if (!CloseClipboard()) { throw new System.Runtime.InteropServices.ExternalException("Could not close Clipboard", new Win32Exception()); } g.ReleaseHdc(hBitmapDC); } } private void __copyMenuItem_Click(object sender, EventArgs e) { using (Graphics g = __pictureBox.CreateGraphics()) { IntPtr hDC = g.GetHdc(); MemoryStream ms = new MemoryStream(); __pictureBox.Image.Save(ms, ImageFormat.Png); ms.Seek(0, SeekOrigin.Begin); Image imag = Image.FromStream(ms); // Derive BitMap object using Image instance, so that you can avoid the issue //"a graphics object cannot be created from an image that has an indexed pixel format" Bitmap img = new Bitmap(new Bitmap(imag)); SetClipboardData(img, hDC); g.ReleaseHdc(); } }

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  • boost::asio::async_write problem

    - by user368831
    Hi, I'm trying to figure out how asynchronous reads and writes work in boost asio by manipulating the echo example. Currently, I have a server that should, when sent a sentence, respond with only the first word. However, the boost::asio::async_write never seems to complete even though the write handler is being called. Can someone please explain what's going on? Here's the code: #include <cstdlib> #include <iostream> #include <boost/bind.hpp> #include <boost/asio.hpp> using boost::asio::ip::tcp; class session { public: session(boost::asio::io_service& io_service) : socket_(io_service) { } tcp::socket& socket() { return socket_; } void start() { std::cout<<"starting"<<std::endl; boost::asio::async_read_until(socket_, buffer, ' ', boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } void handle_read(const boost::system::error_code& error, size_t bytes_transferred) { // std::ostringstream ss; // ss<<&buffer; char* c = new char[bytes_transferred]; //std::string s; buffer.sgetn(c,bytes_transferred); std::cout<<"data: "<< c<<" bytes: "<<bytes_transferred<<std::endl; if (!error) { boost::asio::async_write(socket_, boost::asio::buffer(c,bytes_transferred), boost::bind(&session::handle_write, this, boost::asio::placeholders::error)); } else { delete this; } } void handle_write(const boost::system::error_code& error) { std::cout<<"handling write"<<std::endl; if (!error) { } else { delete this; } } private: tcp::socket socket_; boost::asio::streambuf buffer; }; class server { public: server(boost::asio::io_service& io_service, short port) : io_service_(io_service), acceptor_(io_service, tcp::endpoint(tcp::v4(), port)) { session* new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } void handle_accept(session* new_session, const boost::system::error_code& error) { if (!error) { new_session->start(); new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } else { delete new_session; } } private: boost::asio::io_service& io_service_; tcp::acceptor acceptor_; }; int main(int argc, char* argv[]) { try { if (argc != 2) { std::cerr << "Usage: async_tcp_echo_server <port>\n"; return 1; } boost::asio::io_service io_service; using namespace std; // For atoi. server s(io_service, atoi(argv[1])); io_service.run(); } catch (std::exception& e) { std::cerr << "Exception: " << e.what() << "\n"; } return 0; } Thanks!

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  • Entity Framework 4 relationship management in POCO Templates - More lazy than FixupCollection?

    - by Joe Wood
    I've been taking a look at EF4 POCO templates in beta 2. The FixupCollection looks fine for maintaining the model correctness after updating the relationship collection property (i.e. product.Orders it would set the order.Product reference ). But what about support for handling the scenario when some of those Order objects are removed from the context? The use-case of maintaining cascading deletes in the in-memory model. The old Typed DataSet model used to do this by performing the query through the container to derive the relationship results. Like the DataSet, this would require a reference to the ObjectContext inside the entity class so that it could query the top-level Order collection. Better support for Separation of Concerns in the ObjectContext would be required. It looks like EF is not suited to this use-case that DataSets did out of the box.... am I right?

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  • Does boost::asio makes excessive small heap allocations or am I wrong?

    - by Poni
    #include <cstdlib> #include <iostream> #include <boost/bind.hpp> #include <boost/asio.hpp> using boost::asio::ip::tcp; class session { public: session(boost::asio::io_service& io_service) : socket_(io_service) { } tcp::socket& socket() { return socket_; } void start() { socket_.async_read_some(boost::asio::buffer(data_, max_length - 1), boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } void handle_read(const boost::system::error_code& error, size_t bytes_transferred) { if (!error) { data_[bytes_transferred] = '\0'; if(NULL != strstr(data_, "quit")) { this->socket().shutdown(boost::asio::ip::tcp::socket::shutdown_both); this->socket().close(); // how to make this dispatch "handle_read()" with a "disconnected" flag? } else { boost::asio::async_write(socket_, boost::asio::buffer(data_, bytes_transferred), boost::bind(&session::handle_write, this, boost::asio::placeholders::error)); socket_.async_read_some(boost::asio::buffer(data_, max_length - 1), boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } } else { delete this; } } void handle_write(const boost::system::error_code& error) { if (!error) { // } else { delete this; } } private: tcp::socket socket_; enum { max_length = 1024 }; char data_[max_length]; }; class server { public: server(boost::asio::io_service& io_service, short port) : io_service_(io_service), acceptor_(io_service, tcp::endpoint(tcp::v4(), port)) { session* new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } void handle_accept(session* new_session, const boost::system::error_code& error) { if (!error) { new_session->start(); new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } else { delete new_session; } } private: boost::asio::io_service& io_service_; tcp::acceptor acceptor_; }; int main(int argc, char* argv[]) { try { if (argc != 2) { std::cerr << "Usage: async_tcp_echo_server <port>\n"; return 1; } boost::asio::io_service io_service; using namespace std; // For atoi. server s(io_service, atoi(argv[1])); io_service.run(); } catch (std::exception& e) { std::cerr << "Exception: " << e.what() << "\n"; } return 0; } While experimenting with boost::asio I've noticed that within the calls to async_write()/async_read_some() there is a usage of the C++ "new" keyword. Also, when stressing this echo server with a client (1 connection) that sends for example 100,000 times some data, the memory usage of this program is getting higher and higher. What's going on? Will it allocate memory for every call? Or am I wrong? Asking because it doesn't seem right that a server app will allocate, anything. Can I handle it, say with a memory pool? Another side-question: See the "this-socket().close();" ? I want it, as the comment right to it says, to dispatch that same function one last time, with a disconnection error. Need that to do some clean-up. How do I do that? Thank you all gurus (:

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  • reservoir sampling problem

    - by eSKay
    This MSDN article proves the correctness of Reservoir Sampling algorithm as follows: Base case is trivial. For the k+1st case, the probability a given element i with position <= k is in R is s/k. The probability i is replaced is the probability k+1st element is chosen multiplied by i being chosen to be replaced, which is: s/(k+1) * 1/s = 1/(k+1), and prob that i is not replaced is k/k+1. So any given element's probability of lasting after k+1 rounds is: (chosen in k steps, and not removed in k steps) = s/k * k/(k+1), which is s/(k+1). So, when k+1 = n, any element is present with probability s/n. about step 3: What are the k+1 rounds mentioned? What is chosen in k steps, and not removed in k steps? Why are we only calculating this probability for elements that were already in R after the first s steps?

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  • Print "1 followed by googolplex number of zeros" [closed]

    - by Rajan
    Assuming we are not concerned about running time of the program (which is practically infinite for human mortals), we want to print out in base 10, the exact value of 10^(googolplex), one digit at a time (mostly zeros). Describe an algorithm (which can be coded on current day computers), or write a program to do this. Since we cannot practically check the output, so we will rely on collective opinion on the correctness of the program. NOTE : I do not know the solution, or whether a solution exists or not. The problem is my own invention. To those readers who think this is not a CS question... kindly reconsider. This is difficult and bit theoretical but definitely CS.

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  • Declaring CustomViewController?

    - by fuzzygoat
    I have noticed in some of my older apps that in situations where I have added a custom View Controller I have not changed the View Controller class in the application delegate. For example, below I have created a CustomViewController class but have declared viewController as UIViewController. @interface ApplicationAppDelegate: NSObject <UIApplicationDelegate> { UIWindow *window; UIViewController *viewController; } My question is, both work, but for correctness should I be writing this as follows: @class CustomViewController; @interface ApplicationAppDelegate: NSObject <UIApplicationDelegate> { UIWindow *window; CustomViewController *viewController; } gary

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  • STL operator= behavior change with Visual Studio 2010?

    - by augnob
    Hi, I am attempting to compile QtScriptGenerator (gitorious) with Visual Studio 2010 (C++) and have run into a compile error. In searching for a solution, I have seen occasional references to compile breakages introduced since VS2008 due to changes in VS2010's implementation of STL and/or c++0x conformance changes. Any ideas what is happening below, or how I could go about fixing it? If the offending code appeared to be QtScriptGenerator's, I think I would have an easier time fixing it.. but it appears to me that the offending code may be in VS2010's STL implementation and I may be required to create a workaround? PS. I am pretty unfamiliar with templates and STL. I have a background in embedded and console projects where such things have until recently often been avoided to reduce memory consumption and cross-compiler risks. C:\Program Files\Microsoft Visual Studio 10.0\VC\INCLUDE\xutility(275) : error C2679: binary '=' : no operator found which takes a right-hand operand of type 'rpp::pp_output_iterator<_Container>' (or there is no acceptable conversion) with [ _Container=std::string ] c:\qt\qtscriptgenerator\generator\parser\rpp\pp-iterator.h(75): could be 'rpp::pp_output_iterator<_Container> &rpp::pp_output_iterator<_Container>::operator =(const char &)' with [ _Container=std::string ] while trying to match the argument list '(rpp::pp_output_iterator<_Container>, rpp::pp_output_iterator<_Container>)' with [ _Container=std::string ] C:\Program Files\Microsoft Visual Studio 10.0\VC\INCLUDE\xutility(2176) : see reference to function template instantiation '_Iter &std::_Rechecked<_OutIt,_OutIt>(_Iter &,_UIter)' being compiled with [ _Iter=rpp::pp_output_iterator<std::string>, _OutIt=rpp::pp_output_iterator<std::string>, _UIter=rpp::pp_output_iterator<std::string> ] c:\qt\qtscriptgenerator\generator\parser\rpp\pp-internal.h(83) : see reference to function template instantiation '_OutIt std::copy<std::_String_iterator<_Elem,_Traits,_Alloc>,_OutputIterator>(_InIt,_InIt,_OutIt)' being compiled with [ _OutIt=rpp::pp_output_iterator<std::string>, _Elem=char, _Traits=std::char_traits<char>, _Alloc=std::allocator<char>, _OutputIterator=rpp::pp_output_iterator<std::string>, _InIt=std::_String_iterator<char,std::char_traits<char>,std::allocator<char>> ] c:\qt\qtscriptgenerator\generator\parser\rpp\pp-engine-bits.h(500) : see reference to function template instantiation 'void rpp::_PP_internal::output_line<_OutputIterator>(const std::string &,int,_OutputIterator)' being compiled with [ _OutputIterator=rpp::pp_output_iterator<std::string> ] C:\Program Files\Microsoft Visual Studio 10.0\VC\INCLUDE\xutility(275) : error C2582: 'operator =' function is unavailable in 'rpp::pp_output_iterator<_Container>' with [ _Container=std::string ] Here's some context.. pp-internal.h-- #ifndef PP_INTERNAL_H #define PP_INTERNAL_H #include <algorithm> #include <stdio.h> namespace rpp { namespace _PP_internal { .. 68 template <typename _OutputIterator> 69 void output_line(const std::string &__filename, int __line, _OutputIterator __result) 70 { 71 std::string __msg; 72 73 __msg += "# "; 74 75 char __line_descr[16]; 76 pp_snprintf (__line_descr, 16, "%d", __line); 77 __msg += __line_descr; 78 79 __msg += " \""; 80 81 if (__filename.empty ()) 82 __msg += "<internal>"; 83 else 84 __msg += __filename; 85 86 __msg += "\"\n"; 87 std::copy (__msg.begin (), __msg.end (), __result); 88 }

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  • How to get an X11 Window from a Process ID ?

    - by Adam Pierce
    Under Linux, my C++ application is using fork() and execv() to launch multiple instances of OpenOffice so as to view some powerpoint slide shows. This part works. Next I want to be able to move the OpenOffice windows to specific locations on the display. I can do that with the XMoveResizeWindow() function but I need to find the Window for each instance. I have the process ID of each instance, how can I find the X11 Window from that ? UPDATE - Thanks to Andy's suggestion, I have pulled this off. I'm posting the code here to share it with the Stack Overflow community. Unfortunately Open Office does not seem to set the _NET_WM_PID property so this doesn't ultimately solve my problem but it does answer the question. // Attempt to identify a window by name or attribute. // by Adam Pierce <[email protected]> #include <X11/Xlib.h> #include <X11/Xatom.h> #include <iostream> #include <list> using namespace std; class WindowsMatchingPid { public: WindowsMatchingPid(Display *display, Window wRoot, unsigned long pid) : _display(display) , _pid(pid) { // Get the PID property atom. _atomPID = XInternAtom(display, "_NET_WM_PID", True); if(_atomPID == None) { cout << "No such atom" << endl; return; } search(wRoot); } const list<Window> &result() const { return _result; } private: unsigned long _pid; Atom _atomPID; Display *_display; list<Window> _result; void search(Window w) { // Get the PID for the current Window. Atom type; int format; unsigned long nItems; unsigned long bytesAfter; unsigned char *propPID = 0; if(Success == XGetWindowProperty(_display, w, _atomPID, 0, 1, False, XA_CARDINAL, &type, &format, &nItems, &bytesAfter, &propPID)) { if(propPID != 0) { // If the PID matches, add this window to the result set. if(_pid == *((unsigned long *)propPID)) _result.push_back(w); XFree(propPID); } } // Recurse into child windows. Window wRoot; Window wParent; Window *wChild; unsigned nChildren; if(0 != XQueryTree(_display, w, &wRoot, &wParent, &wChild, &nChildren)) { for(unsigned i = 0; i < nChildren; i++) search(wChild[i]); } } }; int main(int argc, char **argv) { if(argc < 2) return 1; int pid = atoi(argv[1]); cout << "Searching for windows associated with PID " << pid << endl; // Start with the root window. Display *display = XOpenDisplay(0); WindowsMatchingPid match(display, XDefaultRootWindow(display), pid); // Print the result. const list<Window> &result = match.result(); for(list<Window>::const_iterator it = result.begin(); it != result.end(); it++) cout << "Window #" << (unsigned long)(*it) << endl; return 0; }

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  • Need Help Setting Transparent Image to Clipboard

    - by AMissico
    I need help setting a transparent image to the clipboard. I keep getting "handle is invalid". Following is the specific code with the complete working project at ftp://missico.net/ImageVisualizer.zip. This is an image Debug Visualizer class library, but I made to run as executable for testing. (Note that window is a toolbox window and show in taskbar is set to false.) I was tired of having to perform a screen capture on the toolbox window, open with an image editor, and then deleting the background added due to the screen capture. So I thought I would quickly put the transparent image onto the clipboard. Well, the problem is...no transparency support for Clipboard.SetImage. Google to the rescue...not quite. This is what I have so far pulled from a number of sources. See the code for the main reference. My problem is the "invalid handle" when using CF_DIBV5. I imagine the problem is related to BITMAPV5HEADER and CreateDIBitmap. Any help from you GDI/GDI+ Wizards would be greatly appreciated. public static void SetClipboardData(Bitmap bitmap, IntPtr hDC) { const uint SRCCOPY = 0x00CC0020; const int CF_DIBV5 = 17; const int CF_BITMAP = 2; //'reference //'http://social.msdn.microsoft.com/Forums/en-US/winforms/thread/816a35f6-9530-442b-9647-e856602cc0e2 IntPtr memDC = CreateCompatibleDC(hDC); IntPtr memBM = CreateCompatibleBitmap(hDC, bitmap.Width, bitmap.Height); SelectObject(memDC, memBM); using (Graphics g = Graphics.FromImage(bitmap)) { IntPtr hBitmapDC = g.GetHdc(); IntPtr hBitmap = bitmap.GetHbitmap(); SelectObject(hBitmapDC, hBitmap); BitBlt(memDC, 0, 0, bitmap.Width, bitmap.Height, hBitmapDC, 0, 0, SRCCOPY); if (!OpenClipboard(IntPtr.Zero)) { throw new System.Runtime.InteropServices.ExternalException("Could not open Clipboard", new Win32Exception()); } if (!EmptyClipboard()) { throw new System.Runtime.InteropServices.ExternalException("Unable to empty Clipboard", new Win32Exception()); } //IntPtr hClipboard = SetClipboardData(CF_BITMAP, memBM); //works but image is not transparent //all my attempts result in SetClipboardData returning hClipboard = IntPtr.Zero IntPtr hClipboard = SetClipboardData(CF_DIBV5, memBM); //because if (hClipboard == IntPtr.Zero) { // InnerException: System.ComponentModel.Win32Exception // Message="The handle is invalid" // ErrorCode=-2147467259 // NativeErrorCode=6 // InnerException: throw new System.Runtime.InteropServices.ExternalException("Could not put data on Clipboard", new Win32Exception()); } if (!CloseClipboard()) { throw new System.Runtime.InteropServices.ExternalException("Could not close Clipboard", new Win32Exception()); } g.ReleaseHdc(hBitmapDC); } } private void __copyMenuItem_Click(object sender, EventArgs e) { //'Applications that I have verified can paste the clipboard custom data format PNG are: //' Word 2003 //' Excel 2003 using (Graphics g = __pictureBox.CreateGraphics()) { IntPtr hDC = g.GetHdc(); MemoryStream ms = new MemoryStream(); __pictureBox.Image.Save(ms, ImageFormat.Png); ms.Seek(0, SeekOrigin.Begin); Image imag = Image.FromStream(ms); // Derive BitMap object using Image instance, so that you can avoid the issue //"a graphics object cannot be created from an image that has an indexed pixel format" Bitmap img = new Bitmap(new Bitmap(imag)); SetClipboardData(img, hDC); g.ReleaseHdc(); } }

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  • Providing multi-version databases for backward compatibility for production applications/databases.

    - by JavaRocky
    How can I manage multiple versions of a database easily? I have some data (as views as selects for data originating in tables from other schemas), which other database may reference using various means including database synonyms & links. I wish to provide a sort of interface/guarantee in-case future for applications/databases which use this data. All of this is for in the event i need to update the views for correctness or applicability inside my database. How can i achieve this in a maintained, controlled and easy way? I am using Oracle 10g if that matters.

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  • I don't understand how work call_once

    - by SABROG
    Please help me understand how work call_once Here is thread-safe code. I don't understand why this need Thread Local Storage and global_epoch variables. Variable _fast_pthread_once_per_thread_epoch can be changed to constant/enum like {FAST_PTHREAD_ONCE_INIT, BEING_INITIALIZED, FINISH_INITIALIZED}. Why needed count calls in global_epoch? I think this code can be rewriting with logc: if flag FINISH_INITIALIZED do nothing, else go to block with mutexes and this all. #ifndef FAST_PTHREAD_ONCE_H #define FAST_PTHREAD_ONCE_H #include #include typedef sig_atomic_t fast_pthread_once_t; #define FAST_PTHREAD_ONCE_INIT SIG_ATOMIC_MAX extern __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; #ifdef __cplusplus extern "C" { #endif extern void fast_pthread_once( pthread_once_t *once, void (*func)(void) ); inline static void fast_pthread_once_inline( fast_pthread_once_t *once, void (*func)(void) ) { fast_pthread_once_t x = *once; /* unprotected access */ if ( x _fast_pthread_once_per_thread_epoch ) { fast_pthread_once( once, func ); } } #ifdef __cplusplus } #endif #endif FAST_PTHREAD_ONCE_H Source fast_pthread_once.c The source is written in C. The lines of the primary function are numbered for reference in the subsequent correctness argument. #include "fast_pthread_once.h" #include static pthread_mutex_t mu = PTHREAD_MUTEX_INITIALIZER; /* protects global_epoch and all fast_pthread_once_t writes */ static pthread_cond_t cv = PTHREAD_COND_INITIALIZER; /* signalled whenever a fast_pthread_once_t is finalized */ #define BEING_INITIALIZED (FAST_PTHREAD_ONCE_INIT - 1) static fast_pthread_once_t global_epoch = 0; /* under mu */ __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; static void check( int x ) { if ( x == 0 ) abort(); } void fast_pthread_once( fast_pthread_once_t *once, void (*func)(void) ) { /*01*/ fast_pthread_once_t x = *once; /* unprotected access */ /*02*/ if ( x _fast_pthread_once_per_thread_epoch ) { /*03*/ check( pthread_mutex_lock(µ) == 0 ); /*04*/ if ( *once == FAST_PTHREAD_ONCE_INIT ) { /*05*/ *once = BEING_INITIALIZED; /*06*/ check( pthread_mutex_unlock(µ) == 0 ); /*07*/ (*func)(); /*08*/ check( pthread_mutex_lock(µ) == 0 ); /*09*/ global_epoch++; /*10*/ *once = global_epoch; /*11*/ check( pthread_cond_broadcast(&cv;) == 0 ); /*12*/ } else { /*13*/ while ( *once == BEING_INITIALIZED ) { /*14*/ check( pthread_cond_wait(&cv;, µ) == 0 ); /*15*/ } /*16*/ } /*17*/ _fast_pthread_once_per_thread_epoch = global_epoch; /*18*/ check (pthread_mutex_unlock(µ) == 0); } } This code from BOOST: #ifndef BOOST_THREAD_PTHREAD_ONCE_HPP #define BOOST_THREAD_PTHREAD_ONCE_HPP // once.hpp // // (C) Copyright 2007-8 Anthony Williams // // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) #include #include #include #include "pthread_mutex_scoped_lock.hpp" #include #include #include namespace boost { struct once_flag { boost::uintmax_t epoch; }; namespace detail { BOOST_THREAD_DECL boost::uintmax_t& get_once_per_thread_epoch(); BOOST_THREAD_DECL extern boost::uintmax_t once_global_epoch; BOOST_THREAD_DECL extern pthread_mutex_t once_epoch_mutex; BOOST_THREAD_DECL extern pthread_cond_t once_epoch_cv; } #define BOOST_ONCE_INITIAL_FLAG_VALUE 0 #define BOOST_ONCE_INIT {BOOST_ONCE_INITIAL_FLAG_VALUE} // Based on Mike Burrows fast_pthread_once algorithm as described in // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2444.html template void call_once(once_flag& flag,Function f) { static boost::uintmax_t const uninitialized_flag=BOOST_ONCE_INITIAL_FLAG_VALUE; static boost::uintmax_t const being_initialized=uninitialized_flag+1; boost::uintmax_t const epoch=flag.epoch; boost::uintmax_t& this_thread_epoch=detail::get_once_per_thread_epoch(); if(epoch #endif I right understand, boost don't use atomic operation, so code from boost not thread-safe?

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  • How to have struct members accessible in different ways

    - by Paul J. Lucas
    I want to have a structure token that has start/end pairs for position, sentence, and paragraph information. I also want the members to be accessible in two different ways: as a start/end pair and individually. Given: struct token { struct start_end { int start; int end; }; start_end pos; start_end sent; start_end para; typedef start_end token::*start_end_ptr; }; I can write a function, say distance(), that computes the distance between any of the three start/end pairs like: int distance( token const &i, token const &j, token::start_end_ptr mbr ) { return (j.*mbr).start - (i.*mbr).end; } and call it like: token i, j; int d = distance( i, j, &token::pos ); that will return the distance of the pos pair. But I can also pass &token::sent or &token::para and it does what I want. Hence, the function is flexible. However, now I also want to write a function, say max(), that computes the maximum value of all the pos.start or all the pos.end or all the sent.start, etc. If I add: typedef int token::start_end::*int_ptr; I can write the function like: int max( list<token> const &l, token::int_ptr p ) { int m = numeric_limits<int>::min(); for ( list<token>::const_iterator i = l.begin(); i != l.end(); ++i ) { int n = (*i).pos.*p; // NOT WHAT I WANT: It hard-codes 'pos' if ( n > m ) m = n; } return m; } and call it like: list<token> l; l.push_back( i ); l.push_back( j ); int m = max( l, &token::start_end::start ); However, as indicated in the comment above, I do not want to hard-code pos. I want the flexibility of accessible the start or end of any of pos, sent, or para that will be passed as a parameter to max(). I've tried several things to get this to work (tried using unions, anonymous unions, etc.) but I can't come up with a data structure that allows the flexibility both ways while having each value stored only once. Any ideas how to organize the token struct so I can have what I want? Attempt at clarification Given struct of pairs of integers, I want to be able to "slice" the data in two distinct ways: By passing a pointer-to-member of a particular start/end pair so that the called function operates on any pair without knowing which pair. The caller decides which pair. By passing a pointer-to-member of a particular int (i.e., only one int of any pair) so that the called function operates on any int without knowing either which int or which pair said int is from. The caller decides which int of which pair. Another example for the latter would be to sum, say, all para.end or all sent.start. Also, and importantly: for #2 above, I'd ideally like to pass only a single pointer-to-member to reduce the burden on the caller. Hence, me trying to figure something out using unions.

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  • Managing several hundred occurrences of NSLocalizedString

    - by Gordon Hughes
    My application has several hundred points of localisation, some of which can be reused many times. To prevent from hunting and pecking through code to find occurrences of a particular NSLocalizedString, I create a macro for each in a header file using the #define preprocessor directive. For example: #define kLocFirstString NSLocalizedString(@"Default Text", @"Comment") #define kLocSecondString NSLocalizedString(@"More Text", @"Another comment") ... When I want to refer to a particular string, I do so by its macro name. This method has been working nicely for me, but I'm concerned that such blatant abuse of #define is frowned upon. From the standpoint of "correctness", should I just inline each NSLocalizedString with the code, or is there another method (extern NSString *aString; perhaps?) that I can use to collect the declarations in one place?

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  • Splitting string on probable English word boundaries

    - by Sean
    I recently used Adobe Acrobat Pro's OCR feature to process a Japanese kanji dictionary. The overall quality of the output is generally quite a bit better than I'd hoped, but word boundaries in the English portions of the text have often been lost. For example, here's one line from my file: softening;weakening(ofthemarket)8 CHANGE [transform] oneselfINTO,takethe form of; disguise oneself I could go around and insert the missing word boundaries everywhere, but this would be adding to what is already a substantial task. I'm hoping that there might exist software which can analyze text like this, where some of the words run together, and split the text on probable word boundaries. Is there such a package? I'm using Emacs, so it'd be extra-sweet if the package in question were already an Emacs package or could be readily integrated into Emacs, so that I could simply put my cursor on a line like the above and repeatedly invoke some command that splits the line on word boundaries in decreasing order of probable correctness.

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  • 42 passed to TerminateProcess, sometimes GetExitCodeProcess returns 0

    - by Emil
    After I get a handle returned by CreateProcess, I call TerminateProcess, passing 42 for the process exit code. Then, I use WaitForSingleObject for the process to terminate, and finally I call GetExitCodeProcess. None of the function calls report errors. The child process is an infinite loop and does not terminate on its own. The problem is that sometimes GetExitCodeProcess returns 42 for the exit code (as it should) and sometimes it returns 0. Any idea why? #include <string> #include <sstream> #include <iostream> #include <assert.h> #include <windows.h> void check_call( bool result, char const * call ); #define CHECK_CALL(call) check_call(call,#call); int main( int argc, char const * argv[] ) { if( argc>1 ) { assert( !strcmp(argv[1],"inf") ); for(;;) { } } int err=0; for( int i=0; i!=200; ++i ) { STARTUPINFO sinfo; ZeroMemory(&sinfo,sizeof(STARTUPINFO)); sinfo.cb=sizeof(STARTUPINFO); PROCESS_INFORMATION pe; char cmd_line[32768]; strcat(strcpy(cmd_line,argv[0])," inf"); CHECK_CALL((CreateProcess(0,cmd_line,0,0,TRUE,0,0,0,&sinfo,&pe)!=0)); CHECK_CALL((CloseHandle(pe.hThread)!=0)); CHECK_CALL((TerminateProcess(pe.hProcess,42)!=0)); CHECK_CALL((WaitForSingleObject(pe.hProcess,INFINITE)==WAIT_OBJECT_0)); DWORD ec=0; CHECK_CALL((GetExitCodeProcess(pe.hProcess,&ec)!=0)); CHECK_CALL((CloseHandle(pe.hProcess)!=0)); err += (ec!=42); } std::cout << err; return 0; } std::string get_last_error_str( DWORD err ) { std::ostringstream s; s << err; LPVOID lpMsgBuf=0; if( FormatMessageA( FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS, 0, err, MAKELANGID(LANG_NEUTRAL,SUBLANG_DEFAULT), (LPSTR)&lpMsgBuf, 0, 0) ) { assert(lpMsgBuf!=0); std::string msg; try { std::string((LPCSTR)lpMsgBuf).swap(msg); } catch( ... ) { } LocalFree(lpMsgBuf); if( !msg.empty() && msg[msg.size()-1]=='\n' ) msg.resize(msg.size()-1); if( !msg.empty() && msg[msg.size()-1]=='\r' ) msg.resize(msg.size()-1); s << ", \"" << msg << '"'; } return s.str(); } void check_call( bool result, char const * call ) { assert(call && *call); if( !result ) { std::cerr << call << " failed.\nGetLastError:" << get_last_error_str(GetLastError()) << std::endl; exit(2); } }

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  • how to avoid returning mocks from a mocked object list

    - by koen
    I'm trying out mock/responsibility driven design. I seem to have problems to avoid returning mocks from mocks in the case of finder objects. An example could be an object that checks whether the bills from last month are paid. It needs a service that retrieves a list of bills for that. So I need to mock that service that retrieves the bills. At the same time I need that mock to return mocked Bills (since I don't want my test to rely on the correctness bill implementation). Is my design flawed? Is there a better way to test this? Or is this the way it will need to be when using finder objects (the finding of the bills in this case)?

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  • Intrinsics program (SSE) - g++ - help needed

    - by Sriram
    Hi all, This is the first time I am posting a question on stackoverflow, so please try and overlook any errors I may have made in formatting my question/code. But please do point the same out to me so I may be more careful. I was trying to write some simple intrinsics routines for the addition of two 128-bit (containing 4 float variables) numbers. I found some code on the net and was trying to get it to run on my system. The code is as follows: //this is a sample Intrinsics program to add two vectors. #include <iostream> #include <iomanip> #include <xmmintrin.h> #include <stdio.h> using namespace std; struct vector4 { float x, y, z, w; }; //functions to operate on them. vector4 set_vector(float x, float y, float z, float w = 0) { vector4 temp; temp.x = x; temp.y = y; temp.z = z; temp.w = w; return temp; } void print_vector(const vector4& v) { cout << " This is the contents of vector: " << endl; cout << " > vector.x = " << v.x << endl; cout << " vector.y = " << v.y << endl; cout << " vector.z = " << v.z << endl; cout << " vector.w = " << v.w << endl; } vector4 sse_vector4_add(const vector4&a, const vector4& b) { vector4 result; asm volatile ( "movl $a, %eax" //move operands into registers. "\n\tmovl $b, %ebx" "\n\tmovups (%eax), xmm0" //move register contents into SSE registers. "\n\tmovups (%ebx), xmm1" "\n\taddps xmm0, xmm1" //add the elements. addps operates on single-precision vectors. "\n\t movups xmm0, result" //move result into vector4 type data. ); return result; } int main() { vector4 a, b, result; a = set_vector(1.1, 2.1, 3.2, 4.5); b = set_vector(2.2, 4.2, 5.6); result = sse_vector4_add(a, b); print_vector(a); print_vector(b); print_vector(result); return 0; } The g++ parameters I use are: g++ -Wall -pedantic -g -march=i386 -msse intrinsics_SSE_example.C -o h The errors I get are as follows: intrinsics_SSE_example.C: Assembler messages: intrinsics_SSE_example.C:45: Error: too many memory references for movups intrinsics_SSE_example.C:46: Error: too many memory references for movups intrinsics_SSE_example.C:47: Error: too many memory references for addps intrinsics_SSE_example.C:48: Error: too many memory references for movups I have spent a lot of time on trying to debug these errors, googled them and so on. I am a complete noob to Intrinsics and so may have overlooked some important things. Any help is appreciated, Thanks, Sriram.

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  • How can I synchronize database access between a write-thread and a read-thread?

    - by Runcible
    My program has two threads: Main execution thread that handles user input and queues up database writes A utility thread that wakes up every second and flushes the writes to the database Inside the main thread, I occasionally need to make reads on the database. When this happens, performance is not important, but correctness is. (In a perfect world, I would be reading from a cache, not making a round-trip to the database - but let's put that aside for the sake of discussion.) How do I make sure that the main thread sees a correct / quiescent database? A standard mutex won't work, since I run the risk of having the main thread grab the mutex before the data gets flushed to the database. This would be a big race condition. What I really want is some sort of mutex that lets the main thread of execution proceed only AFTER the mutex has been grabbed and released once. Does such a thing exist? What's the best way to solve this problem?

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  • Partial string search in boost::multi_index_container

    - by user361699
    I have a struct to store info about persons and multi_index_contaider to store such objects struct person { std::string m_first_name; std::string m_last_name; std::string m_third_name; std::string m_address; std::string m_phone; person(); person(std::string f, std::string l, std::string t = "", std::string a = DEFAULT_ADDRESS, std::string p = DEFAULT_PHONE) : m_first_name(f), m_last_name(l), m_third_name(t), m_address(a), m_phone(p) {} }; typedef multi_index_container , ordered_non_unique, member, member persons_set; operator< and operator<< implementation for person bool operator<(const person &lhs, const person &rhs) { if(lhs.m_last_name == rhs.m_last_name) { if(lhs.m_first_name == rhs.m_first_name) return (lhs.m_third_name < rhs.m_third_name); return (lhs.m_first_name < rhs.m_first_name); } return (lhs.m_last_name < rhs.m_last_name); } std::ostream& operator<<(std::ostream &s, const person &rhs) { s << "Person's last name: " << rhs.m_last_name << std::endl; s << "Person's name: " << rhs.m_first_name << std::endl; if (!rhs.m_third_name.empty()) s << "Person's third name: " << rhs.m_third_name << std::endl; s << "Phone: " << rhs.m_phone << std::endl; s << "Address: " << rhs.m_address << std::endl; return s; } Add several persons into container: person ("Alex", "Johnson", "Somename"); person ("Alex", "Goodspeed"); person ("Petr", "Parker"); person ("Petr", "Goodspeed"); Now I want to find person by lastname (the first member of the second index in multi_index_container) persons_set::nth_index<1::type &names_index = my_set.get<1(); std::pair::type::const_iterator, persons_set::nth_index<1::type::const_iterator n_it = names_index.equal_range("Goodspeed"); std::copy(n_it.first ,n_it.second, std::ostream_iterator(std::cout)); It works great. Both 'Goodspeed' persons are found. Now lets try to find person by a part of a last name: std::pair::type::const_iterator, persons_set::nth_index<1::type::const_iterator n_it = names_index.equal_range("Good"); std::copy(n_it.first ,n_it.second, std::ostream_iterator(std::cout)); This returns nothing, but partial string search works as a charm in std::set. So I can't realize what's the problem. I only wraped strings by a struct. May be operator< implementation? Thanks in advance for any help.

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  • C++ std::vector insert segfault

    - by ArunSaha
    I am writing a test program to understand vector's better. In one of the scenarios, I am trying to insert a value into the vector at a specified position. The code compiles clean. However, on execution, it is throwing a Segmentation Fault from the v8.insert(..) line (see code below). I am confused. Can somebody point me to what is wrong in my code? #define UNIT_TEST(x) assert(x) #define ENSURE(x) assert(x) #include <vector> typedef std::vector< int > intVector; typedef std::vector< int >::iterator intVectorIterator; typedef std::vector< int >::const_iterator intVectorConstIterator; intVectorIterator find( intVector v, int key ); void test_insert(); intVectorIterator find( intVector v, int key ) { for( intVectorIterator it = v.begin(); it != v.end(); ++it ) { if( *it == key ) { return it; } } return v.end(); } void test_insert() { const int values[] = {10, 20, 30, 40, 50}; const size_t valuesLength = sizeof( values ) / sizeof( values[ 0 ] ); size_t index = 0; const int insertValue = 5; intVector v8; for( index = 0; index < valuesLength; ++index ) { v8.push_back( values[ index ] ); } ENSURE( v8.size() == valuesLength ); for( index = 0; index < valuesLength; ++index ) { printf( "index = %u\n", index ); intVectorIterator it = find( v8, values[ index ] ); ENSURE( it != v8.end() ); ENSURE( *it == values[ index ] ); // intVectorIterator itToInsertedItem = v8.insert( it, insertValue ); // line 51 // UNIT_TEST( *itToInsertedItem == insertValue ); } } int main() { test_insert(); return 0; } $ ./a.out index = 0 Segmentation Fault (core dumped) (gdb) bt #0 0xff3a03ec in memmove () from /platform/SUNW,T5140/lib/libc_psr.so.1 #1 0x00012064 in std::__copy_move_backward<false, true, std::random_access_iterator_tag>::__copy_move_b<int> (__first=0x23e48, __last=0x23450, __result=0x23454) at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/stl_algobase.h:575 #2 0x00011f08 in std::__copy_move_backward_a<false, int*, int*> (__first=0x23e48, __last=0x23450, __result=0x23454) at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/stl_algobase.h:595 #3 0x00011d00 in std::__copy_move_backward_a2<false, int*, int*> (__first=0x23e48, __last=0x23450, __result=0x23454) at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/stl_algobase.h:605 #4 0x000119b8 in std::copy_backward<int*, int*> (__first=0x23e48, __last=0x23450, __result=0x23454) at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/stl_algobase.h:640 #5 0x000113ac in std::vector<int, std::allocator<int> >::_M_insert_aux (this=0xffbfeba0, __position=..., __x=@0xffbfebac) at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/vector.tcc:308 #6 0x00011120 in std::vector<int, std::allocator<int> >::insert (this=0xffbfeba0, __position=..., __x=@0xffbfebac) at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/vector.tcc:126 #7 0x00010bc0 in test_insert () at vector_insert_test.cpp:51 #8 0x00010c48 in main () at vector_insert_test.cpp:58 (gdb) q

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  • The shortest way to convert infix expressions to postfix (RPN) in C

    - by kuszi
    Original formulation is given here (you can try also your program for correctness) . Additional rules: 1. The program should read from standard input and write do standard output. 2. The program should return zero to the calling system/program. 3. The program should compile and run with gcc -O2 -lm -s -fomit-frame-pointer. The challenge has some history: the call for short implementations has been announced at the Polish programming contest blog in September 2009. After the contest, the shortest code was 81 chars long. Later on the second call has been made for even shorter code and after the year matix2267 published his solution in 78 bytes: main(c){read(0,&c,1)?c-41&&main(c-40&&(c%96<27||main(c),putchar(c))):exit(0);} Anyone to make it even shorter or prove this is impossible?

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  • Thread-safe blocking queue implementation on .NET

    - by Shrike
    Hello. I'm looking for an implementation of thread-safe blocking queue for .NET. By "thread-safe blocking queue" I mean: - thread-safe access to a queue where Dequeue method call blocks a thread untill other thread puts (Enqueue) some value. By the moment I'v found this one: http://www.eggheadcafe.com/articles/20060414.asp (But it's for .NET 1.1). Could someone comment/criticize correctness of this implementation. Or suggest some another one. Thanks in advance.

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