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  • Trouble Percent-Encoding Spaces in Java

    - by behrk2
    Hi Everyone, I am using the URLUTF8Encoder.java class from W3C (www.w3.org/International/URLUTF8Encoder.java). Currently, it will encode any blank spaces ' ' into plus signs '+'. I am having difficulty modifying the code to percent-encode the blank space into '%20'. Unfortunately, I am not too familiar with hex. Can anyone help me out? I need to modify this snippet... else if (ch == ' ') { // space sbuf.append('+'); in the following code: final static String[] hex = { "%00", "%01", "%02", "%03", "%04", "%05", "%06", "%07", "%08", "%09", "%0A", "%0B", "%0C", "%0D", "%0E", "%0F", "%10", "%11", "%12", "%13", "%14", "%15", "%16", "%17", "%18", "%19", "%1A", "%1B", "%1C", "%1D", "%1E", "%1F", "%20", "%21", "%22", "%23", "%24", "%25", "%26", "%27", "%28", "%29", "%2A", "%2B", "%2C", "%2D", "%2E", "%2F", "%30", "%31", "%32", "%33", "%34", "%35", "%36", "%37", "%38", "%39", "%3A", "%3B", "%3C", "%3D", "%3E", "%3F", "%40", "%41", "%42", "%43", "%44", "%45", "%46", "%47", "%48", "%49", "%4A", "%4B", "%4C", "%4D", "%4E", "%4F", "%50", "%51", "%52", "%53", "%54", "%55", "%56", "%57", "%58", "%59", "%5A", "%5B", "%5C", "%5D", "%5E", "%5F", "%60", "%61", "%62", "%63", "%64", "%65", "%66", "%67", "%68", "%69", "%6A", "%6B", "%6C", "%6D", "%6E", "%6F", "%70", "%71", "%72", "%73", "%74", "%75", "%76", "%77", "%78", "%79", "%7A", "%7B", "%7C", "%7D", "%7E", "%7F", "%80", "%81", "%82", "%83", "%84", "%85", "%86", "%87", "%88", "%89", "%8A", "%8B", "%8C", "%8D", "%8E", "%8F", "%90", "%91", "%92", "%93", "%94", "%95", "%96", "%97", "%98", "%99", "%9A", "%9B", "%9C", "%9D", "%9E", "%9F", "%A0", "%A1", "%A2", "%A3", "%A4", "%A5", "%A6", "%A7", "%A8", "%A9", "%AA", "%AB", "%AC", "%AD", "%AE", "%AF", "%B0", "%B1", "%B2", "%B3", "%B4", "%B5", "%B6", "%B7", "%B8", "%B9", "%BA", "%BB", "%BC", "%BD", "%BE", "%BF", "%C0", "%C1", "%C2", "%C3", "%C4", "%C5", "%C6", "%C7", "%C8", "%C9", "%CA", "%CB", "%CC", "%CD", "%CE", "%CF", "%D0", "%D1", "%D2", "%D3", "%D4", "%D5", "%D6", "%D7", "%D8", "%D9", "%DA", "%DB", "%DC", "%DD", "%DE", "%DF", "%E0", "%E1", "%E2", "%E3", "%E4", "%E5", "%E6", "%E7", "%E8", "%E9", "%EA", "%EB", "%EC", "%ED", "%EE", "%EF", "%F0", "%F1", "%F2", "%F3", "%F4", "%F5", "%F6", "%F7", "%F8", "%F9", "%FA", "%FB", "%FC", "%FD", "%FE", "%FF" }; public static String encode(String s) { StringBuffer sbuf = new StringBuffer(); int len = s.length(); for (int i = 0; i < len; i++) { int ch = s.charAt(i); if ('A' <= ch && ch <= 'Z') { // 'A'..'Z' sbuf.append((char) ch); } else if ('a' <= ch && ch <= 'z') { // 'a'..'z' sbuf.append((char) ch); } else if ('0' <= ch && ch <= '9') { // '0'..'9' sbuf.append((char) ch); } else if (ch == ' ') { // space sbuf.append('+'); } else if (ch == '-' || ch == '_' // unreserved || ch == '.' || ch == '!' || ch == '~' || ch == '*' || ch == '\'' || ch == '(' || ch == ')') { sbuf.append((char) ch); } else if (ch <= 0x007f) { // other ASCII sbuf.append(hex[ch]); } else if (ch <= 0x07FF) { // non-ASCII <= 0x7FF sbuf.append(hex[0xc0 | (ch >> 6)]); sbuf.append(hex[0x80 | (ch & 0x3F)]); } else { // 0x7FF < ch <= 0xFFFF sbuf.append(hex[0xe0 | (ch >> 12)]); sbuf.append(hex[0x80 | ((ch >> 6) & 0x3F)]); sbuf.append(hex[0x80 | (ch & 0x3F)]); } } return sbuf.toString(); } Thanks!

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  • How does versioning work when using Boost Serialization for Derived Classes?

    - by Venkata Adusumilli
    When a Client serializes the following data: InternationalStudent student; student.id("Client ID"); student.firstName("Client First Name"); student.country("Client Country"); the Server receives the following: ID = "Client ID" Country = "Client First Name" instead of the following: ID = "Client ID" Country = "Client Country" The only difference between the Server and Client classes is the First Name of the Student. How can we make the Server ignore First Name recieved from the Client and process the Country? Server Side Classes class Student { public: Student(){} virtual ~Student(){} public: std::string id() { return idM; } void id(std::string id) { idM = id; } protected: friend class boost::serialization::access; protected: std::string idM; protected: template<class A> void serialize(A& archive, const unsigned int /*version*/) { archive & BOOST_SERIALIZATION_NVP(idM); } }; class InternationalStudent : public Student { public: InternationalStudent() {} ~InternationalStudent() {} public: std::string country() { return countryM; } void country(std::string country) { countryM = country; } protected: friend class boost::serialization::access; protected: std::string countryM; protected: template<class A> void serialize(A& archive, const unsigned int /*version*/) { archive & BOOST_SERIALIZATION_NVP(boost::serialization::base_object<Student>(*this)); archive & BOOST_SERIALIZATION_NVP(countryM); } }; Client Side Classes class Student { public: Student(){} virtual ~Student(){} public: std::string id() { return idM; } void id(std::string id) { idM = id; } std::string firstName() { return firstNameM; } void firstName(std::string name) { firstNameM = name; } protected: friend class boost::serialization::access; protected: std::string idM; std::string firstNameM; protected: template<class A> void serialize(A& archive, const unsigned int /*version*/) { archive & BOOST_SERIALIZATION_NVP(idM); if (version >=1) { archive & BOOST_SERIALIZATION_NVP(firstNameM); } } }; BOOST_CLASS_VERSION(Student, 1) class InternationalStudent : public Student { public: InternationalStudent() {} ~InternationalStudent() {} public: std::string country() { return countryM; } void country(std::string country) { countryM = country; } protected: friend class boost::serialization::access; protected: std::string countryM; protected: template<class A> void serialize(A& archive, const unsigned int /*version*/) { archive & BOOST_SERIALIZATION_NVP(boost::serialization::base_object<Student>(*this)); archive & BOOST_SERIALIZATION_NVP(countryM); } };

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  • GLSL Error: failed to preprocess the source. How can I troubleshoot this?

    - by Brent Parker
    I'm trying to learn to play with OpenGL GLSL shaders. I've written a very simple program to simply create a shader and compile it. However, whenever I get to the compile step, I get the error: Error: Preprocessor error Error: failed to preprocess the source. Here's my very simple code: #include <GL/gl.h> #include <GL/glu.h> #include <GL/glut.h> #include <GL/glext.h> #include <time.h> #include <stdio.h> #include <iostream> #include <stdlib.h> using namespace std; const int screenWidth = 640; const int screenHeight = 480; const GLchar* gravity_shader[] = { "#version 140" "uniform float t;" "uniform mat4 MVP;" "in vec4 pos;" "in vec4 vel;" "const vec4 g = vec4(0.0, 0.0, -9.80, 0.0);" "void main() {" " vec4 position = pos;" " position += t*vel + t*t*g;" " gl_Position = MVP * position;" "}" }; double pointX = (double)screenWidth/2.0; double pointY = (double)screenWidth/2.0; void initShader() { GLuint shader = glCreateShader(GL_VERTEX_SHADER); glShaderSource(shader, 1, gravity_shader, NULL); glCompileShader(shader); GLint compiled = true; glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled); if(!compiled) { GLint length; GLchar* log; glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &length); log = (GLchar*)malloc(length); glGetShaderInfoLog(shader, length, &length, log); std::cout << log <<std::endl; free(log); } exit(0); } bool myInit() { initShader(); glClearColor(1.0f, 1.0f, 1.0f, 0.0f); glColor3f(0.0f, 0.0f, 0.0f); glPointSize(1.0); glLineWidth(1.0f); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(0.0, (GLdouble) screenWidth, 0.0, (GLdouble) screenHeight); glEnable(GL_DEPTH_TEST); return true; } int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB); glutInitWindowSize(screenWidth, screenHeight); glutInitWindowPosition(100, 150); glutCreateWindow("Mouse Interaction Display"); myInit(); glutMainLoop(); return 0; } Where am I going wrong? If it helps, I am trying to do this on a Acer Aspire One with an atom processor and integrated Intel video running the latest Ubuntu. It's not very powerful, but then again, this is a very simple shader. Thanks a lot for taking a look!

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  • Can someone code review my small SDL app? Want to make sure I didn't make any beginner mistakes

    - by SDLFunTimes
    In an effort to teach myself the SDL library (hence my stack overflow handle :) ) I wanted to try my hand at a side-scroller. My code is complete but I want some feedback (mostly because I have an atrocious amount of if and else statements for what seems like some simple logic). My "program" is a c++ side-scroller where you move a single sprite across the screen. No jumping, bad guys, guns, scores, levels or anything. I wanted to use this as a base to build up upon. So I figured if my base is wrong I could end up with some pretty bad future apps. It's also multi-threaded. Next up on this I would like to make the person sprite animated (so it looks like he's walking rather than sliding) as well as make the person go faster when the arrow buttons are held down longer). The code is kind of long but here's my main method. There's a link at the bottom for the whole program: #include <iostream> #include "SDL.h" #include "game.hpp" using std::cout; using std::endl; const int SCREENW = 200; const int SCREENH = 200; const int BPP = 32; const int FPS = 24; int event_loop(void* stuff); int display_loop(void* stuff); int main(int argc, char** argv) { SDL_Init(SDL_INIT_EVERYTHING | SDL_INIT_EVENTTHREAD); SDL_Thread* events_thurd; SDL_Thread* display_thurd; SDL_Surface* screen = SDL_SetVideoMode(SCREENW, SCREENH, BPP, SDL_SWSURFACE); SDL_EnableKeyRepeat(SDL_DEFAULT_REPEAT_DELAY, SDL_DEFAULT_REPEAT_INTERVAL); SDL_Event event; Game* thug_aim = new Game(&event, screen, SCREENW, SCREENH, BPP); events_thurd = SDL_CreateThread(event_loop, (void*)thug_aim); display_thurd = SDL_CreateThread(display_loop, (void*)thug_aim); SDL_WaitThread(events_thurd, NULL); SDL_KillThread(display_thurd); delete thug_aim; return 0; } int event_loop(void* stuff) { Game* gamez = (Game*)stuff; SDL_Event* event = gamez->get_event(); while(1) { while(SDL_PollEvent(event)) { if(event->type == SDL_QUIT) { return 0; } else if(event->type == SDL_KEYDOWN) { if(event->key.keysym.sym == SDLK_LEFT || event->key.keysym.sym == SDLK_RIGHT) { gamez->move(event->key.keysym.sym); } } else if(event->type == SDL_KEYUP) { if(event->key.keysym.sym == SDLK_LEFT || event->key.keysym.sym == SDLK_RIGHT) { gamez->stop_move(event->key.keysym.sym); } } else { //not an event that concerns this game } } } } int display_loop(void* stuff) { Game* gamez = (Game*)stuff; double period = 1 / FPS * 1000; Uint32 milli_period = (Uint32)period; //get some of the attributes from gamez SDL_Rect* background_rect = gamez->get_background_rect(); SDL_Rect* person_rect = gamez->get_person_rect(); SDL_Surface* screen = gamez->get_screen(); SDL_Surface* background = gamez->get_background(); SDL_Surface* person = gamez->get_person(); Uint32 start, end; int sleep; while(1) { start = SDL_GetTicks(); //blit background SDL_BlitSurface(background, background_rect, screen, NULL); //blit person SDL_BlitSurface(person, NULL, screen, person_rect); end = SDL_GetTicks(); sleep = milli_period - (end - start); if(sleep < 0) { sleep = 0; } SDL_Delay((Uint32)sleep); if(SDL_Flip(gamez->get_screen()) != 0) { cout << "error drawing to screen: " << SDL_GetError() << endl; } } } Here's the link to the .zip file of all my code (please ignore some of the variable names ;-) ): Anyway can you guys take a look and tell me what you think? url edit: holy crap I didn't know 2shared was such a shitty site. Looking for a better uploader than that or rapidshare / mediafire.

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  • Marshal a C# struct to C++ VARIANT

    - by jortan
    To start with, I'm not very familiar with the COM-technology, this is the first time I'm working with it so bear with me. I'm trying to call a COM-object function from C#. This is the interface in the idl-file: [id(6), helpstring("vConnectInfo=ConnectInfoType")] HRESULT ConnectTarget([in,out] VARIANT* vConnectInfo); This is the interop interface I got after running tlbimp: void ConnectTarget(ref object vConnectInfo); The c++ code in COM object for the target function: STDMETHODIMP PCommunication::ConnectTarget(VARIANT* vConnectInfo) { if (!((vConnectInfo->vt & VT_ARRAY) && (vConnectInfo->vt & VT_BYREF))) { return E_INVALIDARG; } ConnectInfoType *pConnectInfo = (ConnectInfoType *)((*vConnectInfo->pparray)->pvData); ... } This COM-object is running in another process, it is not in a dll. I can add that the COM object is also used from another program written in C++. In that case there is no problem because in C++ a VARIANT is created and pparray-pvData is set to the connInfo data-structure and then the COM-object is called with the VARIANT as parameter. In C#, as I understand, my struct should be marshalled as a VARIANT automatically. These are two methods I've been using (or actually I've tried a lot more...) to call this method from C#: private void method1_Click(object sender, EventArgs e) { pcom.PCom PCom = new pcom.PCom(); pcom.IGeneralManagementServices mgmt = (pcom.IGeneralManagementServices)PCom; m_ci = new ConnectInfoType(); fillConnInfo(ref m_ci); mgmt.ConnectTarget(m_ci); } In the above case the struct gets marshalled as VT_UNKNOWN. This is a simple case and works if the parameter is not a struct (eg. works for int). private void method4_Click(object sender, EventArgs e) { ConnectInfoType ci = new ConnectInfoType(); fillConnInfo(ref ci); pcom PCom = new pcom.PCom(); pcom.IGeneralManagementServices mgmt = (pcom.IGeneralManagementServices)PCom; ParameterModifier[] pms = new ParameterModifier[1]; ParameterModifier pm = new ParameterModifier(1); pm[0] = true; pms[0] = pm; object[] param = new object[1]; param[0] = ci; object[] args = new object[1]; args[0] = param; mgmt.GetType().InvokeMember("ConnectTarget", BindingFlags.InvokeMethod, null, mgmt, args, pms, null, null); } In this case it gets marshalled as VT_ARRAY | VT_BYREF | VT_VARIANT. The problem is that when debugging the "target-function" ConnectTarget I cannot find the data I send in the SAFEARRAY-struct (or in any other place in memory either) What do I do with a VT_VARIANT? Any ideas on how to get my struct-data? Update: The ConnectInfoType struct: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public class ConnectInfoType { public short network; public short nodeNumber; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 51)] public string connTargPassWord; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8)] public string sConnectId; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 16)] public string sConnectPassword; public EnuConnectType eConnectType; public int hConnectHandle; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8)] public string sAccessPassword; }; And the corresponding struct in c++: typedef struct ConnectInfoType { short network; short nodeNumber; char connTargPassWord[51]; char sConnectId[8]; char sConnectPassword[16]; EnuConnectType eConnectType; int hConnectHandle; char sAccessPassword[8]; } ConnectInfoType;

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  • what is the point of escaping quotation marks in php

    - by Jacksta
    Here is a validation script from a book I am learning, Why is escaping the quotation marks necassery? e.g. <option value=\"char\">char</option> <?php //validate important input if ((!$_POST[table_name]) || (!$_POST[num_fields])) { header( "location: show_createtable.html"); exit; } //begin creating form for display $form_block = " <form action=\"do_createtable.php\" method=\"post\"> <input name=\"table_name\" type=\"hidden\" value=\"$_POST[table_name]\"> <table cellspacing=\"5\" cellpadding=\"5\"> <tr> <th>Field Name</th><th>Field Type</th><th>Table Length</th> </tr>"; //count from 0 until you reach the number fo fields for ($i = 0; $i <$_POST[num_fields]; $i++) { $form_block .=" <tr> <td align=center><input type=\"texr\" name=\"field name[]\" size=\"30\"></td> <td align=center> <select name=\"field_type[]\"> <option value=\"char\">char</option> <option value=\"date\">date</option> <option value=\"float\">float</option> <option value=\"int\">int</option> <option value=\"text\">text</option> <option value=\"varchar\">varchar</option> </select> </td> <td align=center><input type=\"text\" name=\"field_length[]\" size=\"5\"> </td> </tr>"; } //finish up the form $form_block .= " <tr> <td align=center colspan=3><input type =\"submit\" value=\"create table\"> </td> </tr> </table> </form>"; ?> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Create a database table: Step 2</title> </head> <body> <h1>defnie fields for <? echo "$_POST[table_name]"; ?> </h1> <? echo "$form_block"; ?> </body> </html>

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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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  • %HOMEPATH% Posh-Git error in Powershell, in ConEmu on Windows 7 64-bit

    - by atwright
    I am always getting the following error in Posh-Git in Powershell, in ConEmu on Windows 7 64-bit: Resolve-Path : Cannot find path 'C:\wamp\www\MobileApps\Backbone\%HOMEPATH%' because it does not exist. At D:\Users\Andy\Documents\WindowsPowerShell\Modules\posh-git\GitUtils.ps1:265 char:13 + $home = Resolve-Path (Invoke-NullCoalescing $Env:HOME ~) + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : ObjectNotFound: (C:\wamp\www\Mob...bone\%HOMEPATH%:String) [Resolve-Path], ItemNotFoundException + FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.ResolvePathComma nd Join-Path : Cannot bind argument to parameter 'Path' because it is null. At D:\Users\Andy\Documents\WindowsPowerShell\Modules\posh-git\GitUtils.ps1:266 char:29 + Resolve-Path (Join-Path $home ".ssh\$File") -ErrorAction SilentlyContinue 2> ... + ~~~~~ + CategoryInfo : InvalidData: (:) [Join-Path], ParameterBindingValidationExc eption + FullyQualifiedErrorId : ParameterArgumentValidationErrorNullNotAllowed,Microsoft.Po werShell.Commands.JoinPathCommand Can anybody advise what might be wrong?

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  • Policy-based template design: How to access certain policies of the class?

    - by dehmann
    I have a class that uses several policies that are templated. It is called Dish in the following example. I store many of these Dishes in a vector (using a pointer to simple base class), but then I'd like to extract and use them. But I don't know their exact types. Here is the code; it's a bit long, but really simple: #include <iostream> #include <vector> struct DishBase { int id; DishBase(int i) : id(i) {} }; std::ostream& operator<<(std::ostream& out, const DishBase& d) { out << d.id; return out; } // Policy-based class: template<class Appetizer, class Main, class Dessert> class Dish : public DishBase { Appetizer appetizer_; Main main_; Dessert dessert_; public: Dish(int id) : DishBase(id) {} const Appetizer& get_appetizer() { return appetizer_; } const Main& get_main() { return main_; } const Dessert& get_dessert() { return dessert_; } }; struct Storage { typedef DishBase* value_type; typedef std::vector<value_type> Container; typedef Container::const_iterator const_iterator; Container container; Storage() { container.push_back(new Dish<int,double,float>(0)); container.push_back(new Dish<double,int,double>(1)); container.push_back(new Dish<int,int,int>(2)); } ~Storage() { // delete objects } const_iterator begin() { return container.begin(); } const_iterator end() { return container.end(); } }; int main() { Storage s; for(Storage::const_iterator it = s.begin(); it != s.end(); ++it){ std::cout << **it << std::endl; std::cout << "Dessert: " << *it->get_dessert() << std::endl; // ?? } return 0; } The tricky part is here, in the main() function: std::cout << "Dessert: " << *it->get_dessert() << std::endl; // ?? How can I access the dessert? I don't even know the Dessert type (it is templated), let alone the complete type of the object that I'm getting from the storage. This is just a toy example, but I think my code reduces to this. I'd just like to pass those Dish classes around, and different parts of the code will access different parts of it (in the example: its appetizer, main dish, or dessert).

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  • Function signature-like expressions as C++ template arguments

    - by Jeff Lee
    I was looking at Don Clugston's FastDelegate mini-library and noticed a weird syntactical trick with the following structure: TemplateClass< void( int, int ) > Object; It almost appears as if a function signature is being used as an argument to a template instance declaration. This technique (whose presence in FastDelegate is apparently due to one Jody Hagins) was used to simplify the declaration of template instances with a semi-arbitrary number of template parameters. To wit, it allowed this something like the following: // A template with one parameter template<typename _T1> struct Object1 { _T1 m_member1; }; // A template with two parameters template<typename _T1, typename _T2> struct Object2 { _T1 m_member1; _T2 m_member2; }; // A forward declaration template<typename _Signature> struct Object; // Some derived types using "function signature"-style template parameters template<typename _Dummy, typename _T1> struct Object<_Dummy(_T1)> : public Object1<_T1> {}; template<typename _Dummy, typename _T1, typename _T2> struct Object<_Dummy(_T1, _T2)> : public Object2<_T1, _T2> {}; // A. "Vanilla" object declarations Object1<int> IntObjectA; Object2<int, char> IntCharObjectA; // B. Nifty, but equivalent, object declarations typedef void UnusedType; Object< UnusedType(int) > IntObjectB; Object< UnusedType(int, char) > IntCharObjectB; // C. Even niftier, and still equivalent, object declarations #define DeclareObject( ... ) Object< UnusedType( __VA_ARGS__ ) > DeclareObject( int ) IntObjectC; DeclareObject( int, char ) IntCharObjectC; Despite the real whiff of hackiness, I find this kind of spoofy emulation of variadic template arguments to be pretty mind-blowing. The real meat of this trick seems to be the fact that I can pass textual constructs like "Type1(Type2, Type3)" as arguments to templates. So here are my questions: How exactly does the compiler interpret this construct? Is it a function signature? Or, is it just a text pattern with parentheses in it? If the former, then does this imply that any arbitrary function signature is a valid type as far as the template processor is concerned? A follow-up question would be that since the above code sample is valid code, why doesn't the C++ standard just allow you to do something like the following, which is does not compile? template<typename _T1> struct Object { _T1 m_member1; }; // Note the class identifier is also "Object" template<typename _T1, typename _T2> struct Object { _T1 m_member1; _T2 m_member2; }; Object<int> IntObject; Object<int, char> IntCharObject;

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  • About the MSDN Documentation on NOTIFYICONDATA's cbSize member

    - by KenC
    I am reading the NOTIFYICONDATA documentation in MSDN. It says the NOTIFYICONDATA structure has a cbSize member should be set to the size of the structure, but NOTIFYICONDATA structure's size has different size in every Shell32.dll, so you should get the Shell32.dll version before setting cbSize. The following quotes from MSDN: If it is version 5.0 or later, initialize the cbSize member as follows. nid.cbSize = sizeof(NOTIFYICONDATA); Setting cbSize to this value enables all the version 5.0 and 6.0 enhancements. For earlier versions, the size of the pre-6.0 structure is given by the NOTIFYICONDATA_V2_SIZE constant and the pre-5.0 structure is given by the NOTIFYICONDATA_V1_SIZE constant. Initialize the cbSize member as follows. nid.cbSize = NOTIFYICONDATA_V2_SIZE; Using this value for cbSize will allow your application to use NOTIFYICONDATA with earlier Shell32.dll versions, although without the version 6.0 enhancements. I found it a bit of vague, because 'sizeof(NOTIFYICONDATA)' has different value in Win98 (using Shell32.dll version 4.x), Win2K (version 5.0) and WinXP (version 6.0). How could it 'enable all version 5.0 and 6.0 enhancements'? So I looked for the definition of NOTIFYICONDATA_V1_SIZE (source code as below), I see: NOTIFYICONDATA_V1_SIZE is for Win 2K (doesn't include 2K) NOTIFYICONDATA_V2_SIZE is for Win XP NOTIFYICONDATA_V3_SIZE is for Vista (not sure if I am right) It's completely different from what MSDN says? and none for Win2K? So, I am totally confused right now. How should I set the cbSize member according to Shell32.dll version? //= = = = = = = = ShellAPI.h = = = = = = = = typedef struct _NOTIFYICONDATAA { DWORD cbSize; HWND hWnd; UINT uID; UINT uFlags; UINT uCallbackMessage; HICON hIcon; #if (NTDDI_VERSION < NTDDI_WIN2K) CHAR szTip[64]; #endif #if (NTDDI_VERSION >= NTDDI_WIN2K) CHAR szTip[128]; DWORD dwState; DWORD dwStateMask; CHAR szInfo[256]; union { UINT uTimeout; UINT uVersion; // used with NIM_SETVERSION, values 0, 3 and 4 } DUMMYUNIONNAME; CHAR szInfoTitle[64]; DWORD dwInfoFlags; #endif #if (NTDDI_VERSION >= NTDDI_WINXP) GUID guidItem; #endif #if (NTDDI_VERSION >= NTDDI_VISTA) HICON hBalloonIcon; #endif } NOTIFYICONDATAA, *PNOTIFYICONDATAA; typedef struct _NOTIFYICONDATAW { DWORD cbSize; HWND hWnd; UINT uID; UINT uFlags; UINT uCallbackMessage; HICON hIcon; #if (NTDDI_VERSION < NTDDI_WIN2K) WCHAR szTip[64]; #endif #if (NTDDI_VERSION >= NTDDI_WIN2K) WCHAR szTip[128]; DWORD dwState; DWORD dwStateMask; WCHAR szInfo[256]; union { UINT uTimeout; UINT uVersion; // used with NIM_SETVERSION, values 0, 3 and 4 } DUMMYUNIONNAME; WCHAR szInfoTitle[64]; DWORD dwInfoFlags; #endif #if (NTDDI_VERSION >= NTDDI_WINXP) GUID guidItem; #endif #if (NTDDI_VERSION >= NTDDI_VISTA) HICON hBalloonIcon; #endif } NOTIFYICONDATAW, *PNOTIFYICONDATAW; #define NOTIFYICONDATAA_V1_SIZE FIELD_OFFSET(NOTIFYICONDATAA, szTip[64]) #define NOTIFYICONDATAW_V1_SIZE FIELD_OFFSET(NOTIFYICONDATAW, szTip[64]) #ifdef UNICODE #define NOTIFYICONDATA_V1_SIZE NOTIFYICONDATAW_V1_SIZE #else #define NOTIFYICONDATA_V1_SIZE NOTIFYICONDATAA_V1_SIZE #endif #define NOTIFYICONDATAA_V2_SIZE FIELD_OFFSET(NOTIFYICONDATAA, guidItem) #define NOTIFYICONDATAW_V2_SIZE FIELD_OFFSET(NOTIFYICONDATAW, guidItem) #ifdef UNICODE #define NOTIFYICONDATA_V2_SIZE NOTIFYICONDATAW_V2_SIZE #else #define NOTIFYICONDATA_V2_SIZE NOTIFYICONDATAA_V2_SIZE #endif #define NOTIFYICONDATAA_V3_SIZE FIELD_OFFSET(NOTIFYICONDATAA, hBalloonIcon) #define NOTIFYICONDATAW_V3_SIZE FIELD_OFFSET(NOTIFYICONDATAW, hBalloonIcon) #ifdef UNICODE #define NOTIFYICONDATA_V3_SIZE NOTIFYICONDATAW_V3_SIZE #else #define NOTIFYICONDATA_V3_SIZE NOTIFYICONDATAA_V3_SIZE #endif (Seems like the code doesn't look good on the web site, but it from ShellAPI.h, all the same)

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  • What container type provides better (average) performance than std::map?

    - by Truncheon
    In the following example a std::map structure is filled with 26 values from A - Z (for key) and 0 - 26 for value. The time taken (on my system) to lookup the last entry (10000000 times) is roughly 250 ms for the vector, and 125 ms for the map. (I compiled using release mode, with O3 option turned on for g++ 4.4) But if for some odd reason I wanted better performance than the std::map, what data structures and functions would I need to consider using? I apologize if the answer seems obvious to you, but I haven't had much experience in the performance critical aspects of C++ programming. UPDATE: This example is rather trivial and hides the true complexity of what I'm trying to achieve. My real world project is a simple scripting language that uses a parser, data tree, and interpreter (instead of a VM stack system). I need to use some kind of data structure (perhaps map) to store the variables names created by script programmers. These are likely to be pretty randomly named, so I need a lookup method that can quickly find a particular key within a (probably) fairly large list of names. #include <ctime> #include <map> #include <vector> #include <iostream> struct mystruct { char key; int value; mystruct(char k = 0, int v = 0) : key(k), value(v) { } }; int find(const std::vector<mystruct>& ref, char key) { for (std::vector<mystruct>::const_iterator i = ref.begin(); i != ref.end(); ++i) if (i->key == key) return i->value; return -1; } int main() { std::map<char, int> mymap; std::vector<mystruct> myvec; for (int i = 'a'; i < 'a' + 26; ++i) { mymap[i] = i - 'a'; myvec.push_back(mystruct(i, i - 'a')); } int pre = clock(); for (int i = 0; i < 10000000; ++i) { find(myvec, 'z'); } std::cout << "linear scan: milli " << clock() - pre << "\n"; pre = clock(); for (int i = 0; i < 10000000; ++i) { mymap['z']; } std::cout << "map scan: milli " << clock() - pre << "\n"; return 0; }

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  • MySQL query, 2 similar servers, 2 minute difference in execution times

    - by mr12086
    I had a similar question on stack overflow, but it seems to be more server/mysql setup related than coding. The queries below all execute instantly on our development server where as they can take upto 2 minutes 20 seconds. The query execution time seems to be affected by home ambiguous the LIKE string's are. If they closely match a country that has few matches it will take less time, and if you use something like 'ge' for germany - it will take longer to execute. But this doesn't always work out like that, at times its quite erratic. Sending data appears to be the culprit but why and what does that mean. Also memory on production looks to be quite low (free memory)? Production: Intel Quad Xeon E3-1220 3.1GHz 4GB DDR3 2x 1TB SATA in RAID1 Network speed 100Mb Ubuntu Development Intel Core i3-2100, 2C/4T, 3.10GHz 500 GB SATA - No RAID 4GB DDR3 UPDATE 2 : mysqltuner output: [prod] -------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.1.61-0ubuntu0.10.04.1 [OK] Operating on 64-bit architecture -------- Storage Engine Statistics ------------------------------------------- [--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 103M (Tables: 180) [--] Data in InnoDB tables: 491M (Tables: 19) [!!] Total fragmented tables: 38 -------- Security Recommendations ------------------------------------------- [OK] All database users have passwords assigned -------- Performance Metrics ------------------------------------------------- [--] Up for: 77d 4h 6m 1s (53M q [7.968 qps], 14M conn, TX: 87B, RX: 12B) [--] Reads / Writes: 98% / 2% [--] Total buffers: 58.0M global + 2.7M per thread (151 max threads) [OK] Maximum possible memory usage: 463.8M (11% of installed RAM) [OK] Slow queries: 0% (12K/53M) [OK] Highest usage of available connections: 22% (34/151) [OK] Key buffer size / total MyISAM indexes: 16.0M/10.6M [OK] Key buffer hit rate: 98.7% (162M cached / 2M reads) [OK] Query cache efficiency: 20.7% (7M cached / 36M selects) [!!] Query cache prunes per day: 3934 [OK] Sorts requiring temporary tables: 1% (3K temp sorts / 230K sorts) [!!] Joins performed without indexes: 71068 [OK] Temporary tables created on disk: 24% (3M on disk / 13M total) [OK] Thread cache hit rate: 99% (690 created / 14M connections) [!!] Table cache hit rate: 0% (64 open / 85M opened) [OK] Open file limit used: 12% (128/1K) [OK] Table locks acquired immediately: 99% (16M immediate / 16M locks) [!!] InnoDB data size / buffer pool: 491.9M/8.0M -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance Enable the slow query log to troubleshoot bad queries Adjust your join queries to always utilize indexes Increase table_cache gradually to avoid file descriptor limits Variables to adjust: query_cache_size (> 16M) join_buffer_size (> 128.0K, or always use indexes with joins) table_cache (> 64) innodb_buffer_pool_size (>= 491M) [dev] -------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.1.62-0ubuntu0.11.10.1 [!!] Switch to 64-bit OS - MySQL cannot currently use all of your RAM -------- Storage Engine Statistics ------------------------------------------- [--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 185M (Tables: 632) [--] Data in InnoDB tables: 967M (Tables: 38) [!!] Total fragmented tables: 73 -------- Security Recommendations ------------------------------------------- [OK] All database users have passwords assigned -------- Performance Metrics ------------------------------------------------- [--] Up for: 1d 2h 26m 9s (5K q [0.058 qps], 1K conn, TX: 4M, RX: 1M) [--] Reads / Writes: 99% / 1% [--] Total buffers: 58.0M global + 2.7M per thread (151 max threads) [OK] Maximum possible memory usage: 463.8M (11% of installed RAM) [OK] Slow queries: 0% (0/5K) [OK] Highest usage of available connections: 1% (2/151) [OK] Key buffer size / total MyISAM indexes: 16.0M/18.6M [OK] Key buffer hit rate: 99.9% (60K cached / 36 reads) [OK] Query cache efficiency: 44.5% (1K cached / 2K selects) [OK] Query cache prunes per day: 0 [OK] Sorts requiring temporary tables: 0% (0 temp sorts / 44 sorts) [OK] Temporary tables created on disk: 24% (162 on disk / 666 total) [OK] Thread cache hit rate: 99% (2 created / 1K connections) [!!] Table cache hit rate: 1% (64 open / 4K opened) [OK] Open file limit used: 8% (88/1K) [OK] Table locks acquired immediately: 100% (1K immediate / 1K locks) [!!] InnoDB data size / buffer pool: 967.7M/8.0M -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance Enable the slow query log to troubleshoot bad queries Increase table_cache gradually to avoid file descriptor limits Variables to adjust: table_cache (> 64) innodb_buffer_pool_size (>= 967M) UPDATE 1: When testing the queries listed here there is usually no more than one other query taking place, and usually none. Because production is actually handling apache requests that development gets very few of as it's only myself and 1 other who accesses it - could the 4GB of RAM be getting exhausted by using the single machine for both apache and mysql server? Production: sudo hdparm -tT /dev/sda /dev/sda: Timing cached reads: 24872 MB in 2.00 seconds = 12450.72 MB/sec Timing buffered disk reads: 368 MB in 3.00 seconds = 122.49 MB/sec sudo hdparm -tT /dev/sdb /dev/sdb: Timing cached reads: 24786 MB in 2.00 seconds = 12407.22 MB/sec Timing buffered disk reads: 350 MB in 3.00 seconds = 116.53 MB/sec Server version(mysql + ubuntu versions): 5.1.61-0ubuntu0.10.04.1 Development: sudo hdparm -tT /dev/sda /dev/sda: Timing cached reads: 10632 MB in 2.00 seconds = 5319.40 MB/sec Timing buffered disk reads: 400 MB in 3.01 seconds = 132.85 MB/sec Server version(mysql + ubuntu versions): 5.1.62-0ubuntu0.11.10.1 ORIGINAL DATA : This query is NOT the query in question but is related so ill post it. SELECT f.form_question_has_answer_id FROM form_question_has_answer f INNER JOIN project_company_has_user p ON f.form_question_has_answer_user_id = p.project_company_has_user_user_id INNER JOIN company c ON p.project_company_has_user_company_id = c.company_id INNER JOIN project p2 ON p.project_company_has_user_project_id = p2.project_id INNER JOIN user u ON p.project_company_has_user_user_id = u.user_id INNER JOIN form f2 ON p.project_company_has_user_project_id = f2.form_project_id WHERE (f2.form_template_name = 'custom' AND p.project_company_has_user_garbage_collection = 0 AND p.project_company_has_user_project_id = '29') AND (LCASE(c.company_country) LIKE '%ge%' OR LCASE(c.company_country) LIKE '%abcde%') AND f.form_question_has_answer_form_id = '174' And the explain plan for the above query is, run on both dev and production produce the same plan. +----+-------------+-------+--------+----------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+----------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+-------------+ | 1 | SIMPLE | p2 | const | PRIMARY | PRIMARY | 4 | const | 1 | Using index | | 1 | SIMPLE | f | ref | form_question_has_answer_form_id,form_question_has_answer_user_id | form_question_has_answer_form_id | 4 | const | 796 | Using where | | 1 | SIMPLE | u | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.f.form_question_has_answer_user_id | 1 | Using index | | 1 | SIMPLE | p | ref | project_company_has_user_unique_key,project_company_has_user_user_id,project_company_has_user_company_id,project_company_has_user_project_id | project_company_has_user_user_id | 4 | new_klarents.f.form_question_has_answer_user_id | 1 | Using where | | 1 | SIMPLE | f2 | ref | form_project_id | form_project_id | 4 | const | 15 | Using where | | 1 | SIMPLE | c | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.p.project_company_has_user_company_id | 1 | Using where | +----+-------------+-------+--------+----------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+-------------+ This query takes 2 minutes ~20 seconds to execute. The query that is ACTUALLY being run on the server is this one: SELECT COUNT(*) AS num_results FROM (SELECT f.form_question_has_answer_id FROM form_question_has_answer f INNER JOIN project_company_has_user p ON f.form_question_has_answer_user_id = p.project_company_has_user_user_id INNER JOIN company c ON p.project_company_has_user_company_id = c.company_id INNER JOIN project p2 ON p.project_company_has_user_project_id = p2.project_id INNER JOIN user u ON p.project_company_has_user_user_id = u.user_id INNER JOIN form f2 ON p.project_company_has_user_project_id = f2.form_project_id WHERE (f2.form_template_name = 'custom' AND p.project_company_has_user_garbage_collection = 0 AND p.project_company_has_user_project_id = '29') AND (LCASE(c.company_country) LIKE '%ge%' OR LCASE(c.company_country) LIKE '%abcde%') AND f.form_question_has_answer_form_id = '174' GROUP BY f.form_question_has_answer_id;) dctrn_count_query; With explain plans (again same on dev and production): +----+-------------+-------+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+------------------------------+ | 1 | PRIMARY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Select tables optimized away | | 2 | DERIVED | p2 | const | PRIMARY | PRIMARY | 4 | | 1 | Using index | | 2 | DERIVED | f | ref | form_question_has_answer_form_id,form_question_has_answer_user_id | form_question_has_answer_form_id | 4 | | 797 | Using where | | 2 | DERIVED | p | ref | project_company_has_user_unique_key,project_company_has_user_user_id,project_company_has_user_company_id,project_company_has_user_project_id,project_company_has_user_garbage_collection | project_company_has_user_user_id | 4 | new_klarents.f.form_question_has_answer_user_id | 1 | Using where | | 2 | DERIVED | f2 | ref | form_project_id | form_project_id | 4 | | 15 | Using where | | 2 | DERIVED | c | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.p.project_company_has_user_company_id | 1 | Using where | | 2 | DERIVED | u | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.p.project_company_has_user_user_id | 1 | Using where; Using index | +----+-------------+-------+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+------------------------------+ On the production server the information I have is as follows. Upon execution: +-------------+ | num_results | +-------------+ | 3 | +-------------+ 1 row in set (2 min 14.28 sec) Show profile: +--------------------------------+------------+ | Status | Duration | +--------------------------------+------------+ | starting | 0.000016 | | checking query cache for query | 0.000057 | | Opening tables | 0.004388 | | System lock | 0.000003 | | Table lock | 0.000036 | | init | 0.000030 | | optimizing | 0.000016 | | statistics | 0.000111 | | preparing | 0.000022 | | executing | 0.000004 | | Sorting result | 0.000002 | | Sending data | 136.213836 | | end | 0.000007 | | query end | 0.000002 | | freeing items | 0.004273 | | storing result in query cache | 0.000010 | | logging slow query | 0.000001 | | logging slow query | 0.000002 | | cleaning up | 0.000002 | +--------------------------------+------------+ On development the results are as follows. +-------------+ | num_results | +-------------+ | 3 | +-------------+ 1 row in set (0.08 sec) Again the profile for this query: +--------------------------------+----------+ | Status | Duration | +--------------------------------+----------+ | starting | 0.000022 | | checking query cache for query | 0.000148 | | Opening tables | 0.000025 | | System lock | 0.000008 | | Table lock | 0.000101 | | optimizing | 0.000035 | | statistics | 0.001019 | | preparing | 0.000047 | | executing | 0.000008 | | Sorting result | 0.000005 | | Sending data | 0.086565 | | init | 0.000015 | | optimizing | 0.000006 | | executing | 0.000020 | | end | 0.000004 | | query end | 0.000004 | | freeing items | 0.000028 | | storing result in query cache | 0.000005 | | removing tmp table | 0.000008 | | closing tables | 0.000008 | | logging slow query | 0.000002 | | cleaning up | 0.000005 | +--------------------------------+----------+ If i remove user and/or project innerjoins the query is reduced to 30s. Last bit of information I have: Mysqlserver and Apache are on the same box, there is only one box for production. Production output from top: before & after. top - 15:43:25 up 78 days, 12:11, 4 users, load average: 1.42, 0.99, 0.78 Tasks: 162 total, 2 running, 160 sleeping, 0 stopped, 0 zombie Cpu(s): 0.1%us, 50.4%sy, 0.0%ni, 49.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4037868k total, 3772580k used, 265288k free, 243704k buffers Swap: 3905528k total, 265384k used, 3640144k free, 1207944k cached top - 15:44:31 up 78 days, 12:13, 4 users, load average: 1.94, 1.23, 0.87 Tasks: 160 total, 2 running, 157 sleeping, 0 stopped, 1 zombie Cpu(s): 0.2%us, 50.6%sy, 0.0%ni, 49.3%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4037868k total, 3834300k used, 203568k free, 243736k buffers Swap: 3905528k total, 265384k used, 3640144k free, 1207804k cached But this isn't a good representation of production's normal status so here is a grab of it from today outside of executing the queries. top - 11:04:58 up 79 days, 7:33, 4 users, load average: 0.39, 0.58, 0.76 Tasks: 156 total, 1 running, 155 sleeping, 0 stopped, 0 zombie Cpu(s): 3.3%us, 2.8%sy, 0.0%ni, 93.9%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4037868k total, 3676136k used, 361732k free, 271480k buffers Swap: 3905528k total, 268736k used, 3636792k free, 1063432k cached Development: This one doesn't change during or after. top - 15:47:07 up 110 days, 22:11, 7 users, load average: 0.17, 0.07, 0.06 Tasks: 210 total, 2 running, 208 sleeping, 0 stopped, 0 zombie Cpu(s): 0.1%us, 0.2%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4111972k total, 1821100k used, 2290872k free, 238860k buffers Swap: 4183036k total, 66472k used, 4116564k free, 921072k cached

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  • Why is the this-pointer needed to access inherited attributes?

    - by Shadow
    Hi, assume the following class is given: class Base{ public: Base() {} Base( const Base& b) : base_attr(b.base_attr) {} void someBaseFunction() { .... } protected: SomeType base_attr; }; When I want a class to inherit from this one and include a new attribute for the derived class, I would write: class Derived: public Base { public: Derived() {} Derived( const Derived& d ) : derived_attr(d.derived_attr) { this->base_attr = d.base_attr; } void SomeDerivedFunction() { .... } private: SomeOtherType derived_attr; }; This works for me (let's ignore eventually missing semicolons or such please). However, when I remove the "this-" in the copy constructor of the derived class, the compiler complains that "'base_attr' was not declared in this scope". I thought that, when inheriting from a class, the protected attributes would then also be accessible directly. I did not know that the "this-" pointer was needed. I am now confused if it is actually correct what I am doing there, especially the copy-constructor of the Derived-class. Because each Derived object is supposed to have a base_attr and a derived_attr and they obviously need to be initialized/set correctly. And because Derived is inheriting from Base, I don't want to explicitly include an attribute named "base_attr" in the Derived-class. IMHO doing so would generally destroy the idea behind inheritance, as everything would have to be defined again. EDIT Thank you all for the quick answers. I completely forgot the fact that the classes actually are templates. Please, see the new examples below, which are actually compiling when including "this-" and are failing when omiting "this-" in the copy-constructor of the Derived-class: Base-class: #include <iostream> template<class T> class Base{ public: Base() : base_attr(0) {} Base( const Base& b) : base_attr(b.base_attr) {} void baseIncrement() { ++base_attr; } void printAttr() { std::cout << "Base Attribute: " << base_attr << std::endl; } protected: T base_attr; }; Derived-class: #include "base.hpp" template< class T > class Derived: public Base<T>{ public: Derived() : derived_attr(1) {} Derived( const Derived& d) : derived_attr(d.derived_attr) { this->base_attr = d.base_attr; } void derivedIncrement() { ++derived_attr; } protected: T derived_attr; }; and for completeness also the main function: #include "derived.hpp" int main() { Derived<int> d; d.printAttr(); d.baseIncrement(); d.printAttr(); Derived<int> d2(d); d2.printAttr(); return 0; }; I am using g++-4.3.4. Although I understood now that it seems to come from the fact that I use template-class definitions, I did not quite understand what is causing the problem when using templates and why it works when not using templates. Could someone please further clarify this?

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  • [C] Texture management / pointer question

    - by ndg
    I'm working on a texture management and animation solution for a small side project of mine. Although the project uses Allegro for rendering and input, my question mostly revolves around C and memory management. I wanted to post it here to get thoughts and insight into the approach, as I'm terrible when it comes to pointers. Essentially what I'm trying to do is load all of my texture resources into a central manager (textureManager) - which is essentially an array of structs containing ALLEGRO_BITMAP objects. The textures stored within the textureManager are mostly full sprite sheets. From there, I have an anim(ation) struct, which contains animation-specific information (along with a pointer to the corresponding texture within the textureManager). To give you an idea, here's how I setup and play the players 'walk' animation: createAnimation(&player.animations[0], "media/characters/player/walk.png", player.w, player.h); playAnimation(&player.animations[0], 10); Rendering the animations current frame is just a case of blitting a specific region of the sprite sheet stored in textureManager. For reference, here's the code for anim.h and anim.c. I'm sure what I'm doing here is probably a terrible approach for a number of reasons. I'd like to hear about them! Am I opening myself to any pitfalls? Will this work as I'm hoping? anim.h #ifndef ANIM_H #define ANIM_H #define ANIM_MAX_FRAMES 10 #define MAX_TEXTURES 50 struct texture { bool active; ALLEGRO_BITMAP *bmp; }; struct texture textureManager[MAX_TEXTURES]; typedef struct tAnim { ALLEGRO_BITMAP **sprite; int w, h; int curFrame, numFrames, frameCount; float delay; } anim; void setupTextureManager(void); int addTexture(char *filename); int createAnimation(anim *a, char *filename, int w, int h); void playAnimation(anim *a, float delay); void updateAnimation(anim *a); #endif anim.c void setupTextureManager() { int i = 0; for(i = 0; i < MAX_TEXTURES; i++) { textureManager[i].active = false; } } int addTextureToManager(char *filename) { int i = 0; for(i = 0; i < MAX_TEXTURES; i++) { if(!textureManager[i].active) { textureManager[i].bmp = al_load_bitmap(filename); textureManager[i].active = true; if(!textureManager[i].bmp) { printf("Error loading texture: %s", filename); return -1; } return i; } } return -1; } int createAnimation(anim *a, char *filename, int w, int h) { int textureId = addTextureToManager(filename); if(textureId > -1) { a->sprite = textureManager[textureId].bmp; a->w = w; a->h = h; a->numFrames = al_get_bitmap_width(a->sprite) / w; printf("Animation loaded with %i frames, given resource id: %i\n", a->numFrames, textureId); } else { printf("Texture manager full\n"); return 1; } return 0; } void playAnimation(anim *a, float delay) { a->curFrame = 0; a->frameCount = 0; a->delay = delay; } void updateAnimation(anim *a) { a->frameCount ++; if(a->frameCount >= a->delay) { a->frameCount = 0; a->curFrame ++; if(a->curFrame >= a->numFrames) { a->curFrame = 0; } } }

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  • STL find performs bettern than hand-crafter loop

    - by dusha
    Hello all, I have some question. Given the following C++ code fragment: #include <boost/progress.hpp> #include <vector> #include <algorithm> #include <numeric> #include <iostream> struct incrementor { incrementor() : curr_() {} unsigned int operator()() { return curr_++; } private: unsigned int curr_; }; template<class Vec> char const* value_found(Vec const& v, typename Vec::const_iterator i) { return i==v.end() ? "no" : "yes"; } template<class Vec> typename Vec::const_iterator find1(Vec const& v, typename Vec::value_type val) { return find(v.begin(), v.end(), val); } template<class Vec> typename Vec::const_iterator find2(Vec const& v, typename Vec::value_type val) { for(typename Vec::const_iterator i=v.begin(), end=v.end(); i<end; ++i) if(*i==val) return i; return v.end(); } int main() { using namespace std; typedef vector<unsigned int>::const_iterator iter; vector<unsigned int> vec; vec.reserve(10000000); boost::progress_timer pt; generate_n(back_inserter(vec), vec.capacity(), incrementor()); //added this line, to avoid any doubts, that compiler is able to // guess the data is sorted random_shuffle(vec.begin(), vec.end()); cout << "value generation required: " << pt.elapsed() << endl; double d; pt.restart(); iter found=find1(vec, vec.capacity()); d=pt.elapsed(); cout << "first search required: " << d << endl; cout << "first search found value: " << value_found(vec, found)<< endl; pt.restart(); found=find2(vec, vec.capacity()); d=pt.elapsed(); cout << "second search required: " << d << endl; cout << "second search found value: " << value_found(vec, found)<< endl; return 0; } On my machine (Intel i7, Windows Vista) STL find (call via find1) runs about 10 times faster than the hand-crafted loop (call via find2). I first thought that Visual C++ performs some kind of vectorization (may be I am mistaken here), but as far as I can see assembly does not look the way it uses vectorization. Why is STL loop faster? Hand-crafted loop is identical to the loop from the STL-find body. I was asked to post program's output. Without shuffle: value generation required: 0.078 first search required: 0.008 first search found value: no second search required: 0.098 second search found value: no With shuffle (caching effects): value generation required: 1.454 first search required: 0.009 first search found value: no second search required: 0.044 second search found value: no Many thanks, dusha. P.S. I return the iterator and write out the result (found or not), because I would like to prevent compiler optimization, that it thinks the loop is not required at all. The searched value is obviously not in the vector.

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  • How to map code points to unicode characters depending on the font used?

    - by Alex Schröder
    The client prints labels and has been using a set of symbolic (?) fonts to do this. The application uses a single byte database (Oracle with Latin-1). The old application I am replacing was not Unicode aware. It somehow did OK. The replacement application I am writing is supposed to handle the old data. The symbols picked from the charmap application often map to particular Unicode characters, but sometimes they don't. What looks like the Moon using the LAB3 font, for example, is in fact U+2014 (EM DASH). When users paste this character into a Swing text field, the character has the code point 8212. It was "moved" into the Private Use Area (by Windows? Java?). When saving this character to the database, Oracle decides that it cannot be safely encoded and replaces it with the dreaded ¿. Thus, I started shifting the characters by 8000: -= 8000 when saving, += 8000 when displaying the field. Unfortunately I discovered that other characters were not shifted by the same amount. In one particular font, for example, ž has the code point 382, so I shifted it by +/-256 to "fix" it. By now I'm dreading the discovery of more strange offsets and I wonder: Can I get at this mapping using Java? Perhaps the TTF font has a list of the 255 glyphs it encodes and what Unicode characters those correspond to and I can do it "right"? Right now I'm using the following kludge: static String fromDatabase(String str, String fontFamily) { if (str != null && fontFamily != null) { Font font = new Font(fontFamily, Font.PLAIN, 1); boolean changed = false; char[] chars = str.toCharArray(); for (int i = 0; i < chars.length; i++) { if (font.canDisplay(chars[i] + 0xF000)) { // WE8MSWIN1252 + WinXP chars[i] += 0xF000; changed = true; } else if (chars[i] >= 128 && font.canDisplay(chars[i] + 8000)) { // WE8ISO8859P1 + WinXP chars[i] += 8000; changed = true; } else if (font.canDisplay(chars[i] + 256)) { // ž in LAB1 Eastern = 382 chars[i] += 256; changed = true; } } if (changed) str = new String(chars); } return str; } static String toDatabase(String str, String fontFamily) { if (str != null && fontFamily != null) { boolean changed = false; char[] chars = str.toCharArray(); for (int i = 0; i < chars.length; i++) { int chr = chars[i]; if (chars[i] > 0xF000) { // WE8MSWIN1252 + WinXP chars[i] -= 0xF000; changed = true; } else if (chars[i] > 8000) { // WE8ISO8859P1 + WinXP chars[i] = (char) (chars[i] - 8000); changed = true; } else if (chars[i] > 256) { // ž in LAB1 Eastern = 382 chars[i] = (char) (chars[i] - 256); changed = true; } } if (changed) return new String(chars); } return str; }

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  • C++ Greatest Number Verification

    - by Daniel
    Hey guys, I was assigned to create a program that creates n arrays composed by 10 random integers. The the program should sum all the integers and display the result. After, it has to verify which of the sums is the greatest and it has to display that array and the result. Im having troubles getting it done and would like to get some help! Thanks once again. Here is my code so far: #include <iostream> #include <iomanip> #include <cmath> using namespace std; double random(unsigned int &seed); unsigned int seed = 5; void generateData(int set[10]); int sumData(int set[10]); void checkData(int sumResult, int arrayNumber); int main (int argc, char * const argv[]) { int arrayNumber, sumResult; int set[10]; do { cout << "Number of Arrays to Compare: " << endl; cin >> arrayNumber; } while (arrayNumber < 0); for (int i = 0; i < arrayNumber; ++i) { generateData(set); sumResult = sumData(set); cout << "Sum --> " << sumResult << endl; checkData(sumResult, arrayNumber); } return 0; } double random(unsigned int &seed) { const int MODULUS = 15749; const int MULTIPLIER = 69069; const int INCREMENT = 1; seed = ((MULTIPLIER * seed) + INCREMENT) % MODULUS; return double(seed) / double(MODULUS); } void generateData(int set[10]) { for (int i = 0; i < 10; ++i) { set[i] = int (5 + 6 * random(seed)); cout << set[i] << " || "; } } int sumData(int set[10]) { int sumTotal = 0; for (int i = 0; i < 10; ++i) sumTotal = sumTotal + set[i]; return sumTotal; } void checkData(int sumResult, int arrayNumber) { int largerNumber; int tempSet[2]; for (int i = 0; i < arrayNumber; ++i) { if (sumResult > largerNumber) { tempSet[i] = sumResult; } } }

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  • Odd C++ template behaviour with static member vars

    - by jon hanson
    This piece of code is supposed to calculate an approximation to e (i.e. the mathematical constant ~ 2.71828183) at compile-time, using the following approach; e1 = 2 / 1 e2 = (2 * 2 + 1) / (2 * 1) = 5 / 2 = 2.5 e3 = (3 * 5 + 1) / (3 * 2) = 16 / 6 ~ 2.67 e4 = (4 * 16 + 1) / (4 * 6) = 65 / 24 ~ 2.708 ... e(i) = (e(i-1).numer * i + 1) / (e(i-1).denom * i) The computation is returned via the result static member however, after 2 iterations it yields zero instead of the expected value. I've added a static member function f() to compute the same value and that doesn't exhibit the same problem. #include <iostream> #include <iomanip> // Recursive case. template<int ITERS, int NUMERATOR = 2, int DENOMINATOR = 1, int I = 2> struct CalcE { static const double result; static double f () {return CalcE<ITERS, NUMERATOR * I + 1, DENOMINATOR * I, I + 1>::f ();} }; template<int ITERS, int NUMERATOR, int DENOMINATOR, int I> const double CalcE<ITERS, NUMERATOR, DENOMINATOR, I>::result = CalcE<ITERS, NUMERATOR * I + 1, DENOMINATOR * I, I + 1>::result; // Base case. template<int ITERS, int NUMERATOR, int DENOMINATOR> struct CalcE<ITERS, NUMERATOR, DENOMINATOR, ITERS> { static const double result; static double f () {return result;} }; template<int ITERS, int NUMERATOR, int DENOMINATOR> const double CalcE<ITERS, NUMERATOR, DENOMINATOR, ITERS>::result = static_cast<double>(NUMERATOR) / DENOMINATOR; // Test it. int main (int argc, char* argv[]) { std::cout << std::setprecision (8); std::cout << "e2 ~ " << CalcE<2>::result << std::endl; std::cout << "e3 ~ " << CalcE<3>::result << std::endl; std::cout << "e4 ~ " << CalcE<4>::result << std::endl; std::cout << "e5 ~ " << CalcE<5>::result << std::endl; std::cout << std::endl; std::cout << "e2 ~ " << CalcE<2>::f () << std::endl; std::cout << "e3 ~ " << CalcE<3>::f () << std::endl; std::cout << "e4 ~ " << CalcE<4>::f () << std::endl; std::cout << "e5 ~ " << CalcE<5>::f () << std::endl; return 0; } I've tested this with VS 2008 and VS 2010, and get the same results in each case: e2 ~ 2 e3 ~ 2.5 e4 ~ 0 e5 ~ 0 e2 ~ 2 e3 ~ 2.5 e4 ~ 2.6666667 e5 ~ 2.7083333 Why does result not yield the expected values whereas f() does? According to Rotsor's comment below, this does work with GCC, so I guess the question is, am i relying on some type of undefined behaviour with regards to static initialisation order, or is this a bug with Visual Studio?

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  • NSMutableArray memory leak when reloading objects

    - by Davin
    I am using Three20/TTThumbsviewcontroller to load photos. I am struggling since quite a some time now to fix memory leak in setting photosource. I am beginner in Object C & iOS memory management. Please have a look at following code and suggest any obvious mistakes or any errors in declaring and releasing variables. -- PhotoViewController.h @interface PhotoViewController : TTThumbsViewController <UIPopoverControllerDelegate,CategoryPickerDelegate,FilterPickerDelegate,UISearchBarDelegate>{ ...... NSMutableArray *_photoList; ...... @property(nonatomic,retain) NSMutableArray *photoList; -- PhotoViewController.m @implementation PhotoViewController .... @synthesize photoList; ..... - (void)LoadPhotoSource:(NSString *)query:(NSString *)title:(NSString* )stoneName{ NSLog(@"log- in loadPhotosource method"); if (photoList == nil) photoList = [[NSMutableArray alloc] init ]; [photoList removeAllObjects]; @try { sqlite3 *db; NSFileManager *fileMgr = [NSFileManager defaultManager]; NSString* documentsPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; NSString *dbPath = [documentsPath stringByAppendingPathComponent: @"DB.s3db"]; BOOL success = [fileMgr fileExistsAtPath:dbPath]; if(!success) { NSLog(@"Cannot locate database file '%@'.", dbPath); } if(!(sqlite3_open([dbPath UTF8String], &db) == SQLITE_OK)) { NSLog(@"An error has occured."); } NSString *_sql = query;//[NSString stringWithFormat:@"SELECT * FROM Products where CategoryId = %i",[categoryId integerValue]]; const char *sql = [_sql UTF8String]; sqlite3_stmt *sqlStatement; if(sqlite3_prepare(db, sql, -1, &sqlStatement, NULL) != SQLITE_OK) { NSLog(@"Problem with prepare statement"); } if ([stoneName length] != 0) { NSString *wildcardSearch = [NSString stringWithFormat:@"%@%%",[stoneName stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]]; sqlite3_bind_text(sqlStatement, 1, [wildcardSearch UTF8String], -1, SQLITE_STATIC); } while (sqlite3_step(sqlStatement)==SQLITE_ROW) { NSString* urlSmallImage = @"Mahallati_NoImage.png"; NSString* urlThumbImage = @"Mahallati_NoImage.png"; NSString *designNo = [NSString stringWithUTF8String:(char *) sqlite3_column_text(sqlStatement,2)]; designNo = [designNo stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *desc = [NSString stringWithUTF8String:(char *) sqlite3_column_text(sqlStatement,7)]; desc = [desc stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *caption = designNo;//[designNo stringByAppendingString:desc]; caption = [caption stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *smallFilePath = [documentsPath stringByAppendingPathComponent: [NSString stringWithFormat:@"Small%@.JPG",designNo] ]; smallFilePath = [smallFilePath stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; if ([fileMgr fileExistsAtPath:smallFilePath]){ urlSmallImage = [NSString stringWithFormat:@"Small%@.JPG",designNo]; } NSString *thumbFilePath = [documentsPath stringByAppendingPathComponent: [NSString stringWithFormat:@"Thumb%@.JPG",designNo] ]; thumbFilePath = [thumbFilePath stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; if ([fileMgr fileExistsAtPath:thumbFilePath]){ urlThumbImage = [NSString stringWithFormat:@"Thumb%@.JPG",designNo]; } NSNumber *photoProductId = [NSNumber numberWithInt:(int)sqlite3_column_int(sqlStatement, 0)]; NSNumber *photoPrice = [NSNumber numberWithInt:(int)sqlite3_column_int(sqlStatement, 6)]; char *productNo1 = sqlite3_column_text(sqlStatement, 3); NSString* productNo; if (productNo1 == NULL) productNo = nil; else productNo = [NSString stringWithUTF8String:productNo1]; Photo *jphoto = [[[Photo alloc] initWithCaption:caption urlLarge:[NSString stringWithFormat:@"documents://%@",urlSmallImage] urlSmall:[NSString stringWithFormat:@"documents://%@",urlSmallImage] urlThumb:[NSString stringWithFormat:@"documents://%@",urlThumbImage] size:CGSizeMake(123, 123) productId:photoProductId price:photoPrice description:desc designNo:designNo productNo:productNo ] autorelease]; [photoList addObject:jphoto]; [jphoto release]; } } @catch (NSException *exception) { NSLog(@"An exception occured: %@", [exception reason]); } self.photoSource = [[[MockPhotoSource alloc] initWithType:MockPhotoSourceNormal title:[NSString stringWithFormat: @"%@",title] photos: photoList photos2:nil] autorelease]; } Memory leaks happen when calling above LoadPhotosource method again with different query... I feel its something wrong in declaring NSMutableArray (photoList), but can't figure out how to fix memory leak. Any suggestion is really appreciated.

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  • Renaming Nginx 1.3.5 Server: response header

    - by Ryan
    In nginx 1.2 & 1.3 you can modify the source to change the name: src/http/ngx_http_header_filter_module.c (lines 48 and 49): static char ngx_http_server_string[] = "Server: Not Nginx" CRLF; static char ngx_http_server_full_string[] = "Server: Not Nginx/1.0" CRLF; Renaming those and recompiling the source changes the server response name in nginx 1.2. However doing this in 1.3 does not seem to change the name. It still says nginx/1.3.5 and with server_tokens off; it just says nginx. How can I change the server name in 1.3 without installing the 3rd party addon headers more? I want to compile from source.

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  • Display problem after deletion in linked list in C

    - by LuckySlevin
    Hi, actually this was another problem but it changed so I decided to open a new question. My code is typedef struct inner_list { int count; char word[100]; inner_list*next; } inner_list; typedef struct outer_list { char word [100]; inner_list * head; int count; outer_list * next; } outer_list; void delnode(outer_list **head,char num[100])//thanks to both Nir Levy and Jeremy P. { outer_list *temp, *m; m=temp=*head; /*FIX #1*/ while(temp!=NULL) { if(strcmp(temp->word,num)==0) { if(temp==*head) { delinner(temp->head); /* FIX#2 */ *head=temp->next; free(temp); return; } else { delinner(temp->head); /* FIX#2 */ m->next=temp->next; free(temp); return; } } else { m=temp; temp= temp->next; } } printf(" ELEMENT %s NOT FOUND ", num); } void delinner(inner_list *head) { /* FIX#2 */ inner_list *temp; temp=head; while(temp!=NULL) { head=temp->next; free(temp); temp=head; } } void delnode2(outer_list *up,inner_list **head,char num[100]) { inner_list *temp2,*temp, *m; outer_list *p; p = up; while(p!=NULL){m=temp=temp2=p->head; while(temp!=NULL) { if(strcmp(temp->word,num)==0) { if(temp==(*head)) { *head=temp->next; free(temp); return; } else { m->next=temp->next; free(temp); return; } } else { m=temp; temp= temp->next; } } p=p->next; } printf(" ELEMENT %s NOT FOUND ", num); } void print_node(outer_list *parent_node) { while(parent_node!=NULL){ printf("%s\t%d\t", parent_node->word, parent_node->count); inner_list *child_node = parent_node->head; printf("list: "); if(child_node ==NULL){printf("BUARADA");} while (child_node != NULL) { printf("%s-%d", child_node->word,child_node->count); child_node = child_node->next; if (child_node != NULL) { printf("->"); } } printf("\n"); parent_node = parent_node->next; } } While deleting an element from outer list I am also trying the delete the same element from inner_list too. For example: - Let's say aaa is an element of outer_list linked list and let's point it with outer_list *p - This aaa can also be in an inner_list linked list too. (it can be in p-head or another innerlist.) Now, the tricky part again. I tried to apply the same rules with outer_list deletion but whenever i delete the head element of inner_list it gives an error. Where is the wrong thing in print_node or delnode2?

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  • Want to Receive dynamic length data from a message queue in IPC?

    - by user1089679
    Here I have to send and receive dynamic data using a SysV message queue. so in structure filed i have dynamic memory allocation char * because its size may be varies. so how can i receive this type of message at receiver side. Please let me know how can i send dynamic length of data with message queue. I am getting problem in this i posted my code below. send.c /*filename : send.c *To compile : gcc send.c -o send */ #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> struct my_msgbuf { long mtype; char *mtext; }; int main(void) { struct my_msgbuf buf; int msqid; key_t key; static int count = 0; char temp[5]; int run = 1; if ((key = ftok("send.c", 'B')) == -1) { perror("ftok"); exit(1); } printf("send.c Key is = %d\n",key); if ((msqid = msgget(key, 0644 | IPC_CREAT)) == -1) { perror("msgget"); exit(1); } printf("Enter lines of text, ^D to quit:\n"); buf.mtype = 1; /* we don't really care in this case */ int ret = -1; while(run) { count++; buf.mtext = malloc(50); strcpy(buf.mtext,"Hi hello test message here"); snprintf(temp, sizeof (temp), "%d",count); strcat(buf.mtext,temp); int len = strlen(buf.mtext); /* ditch newline at end, if it exists */ if (buf.mtext[len-1] == '\n') buf.mtext[len-1] = '\0'; if (msgsnd(msqid, &buf, len+1, IPC_NOWAIT) == -1) /* +1 for '\0' */ perror("msgsnd"); if(count == 100) run = 0; usleep(1000000); } if (msgctl(msqid, IPC_RMID, NULL) == -1) { perror("msgctl"); exit(1); } return 0; } receive.c /* filename : receive.c * To compile : gcc receive.c -o receive */ #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> struct my_msgbuf { long mtype; char *mtext; }; int main(void) { struct my_msgbuf buf; int msqid; key_t key; if ((key = ftok("send.c", 'B')) == -1) { /* same key as send.c */ perror("ftok"); exit(1); } if ((msqid = msgget(key, 0644)) == -1) { /* connect to the queue */ perror("msgget"); exit(1); } printf("test: ready to receive messages, captain.\n"); for(;;) { /* receive never quits! */ buf.mtext = malloc(50); if (msgrcv(msqid, &buf, 50, 0, 0) == -1) { perror("msgrcv"); exit(1); } printf("test: \"%s\"\n", buf.mtext); } return 0; }

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  • What's the fastest lookup algorithm for a pair data structure (i.e, a map)?

    - by truncheon
    In the following example a std::map structure is filled with 26 values from A - Z (for key) and 0 – 26 for value. The time taken (on my system) to lookup the last entry (10000000 times) is roughly 250 ms for the vector, and 125 ms for the map. (I compiled using release mode, with O3 option turned on for g++ 4.4) But if for some odd reason I wanted better performance than the std::map, what data structures and functions would I need to consider using? I apologize if the answer seems obvious to you, but I haven't had much experience in the performance critical aspects of C++ programming. UPDATE: This example is rather trivial and hides the true complexity of what I'm trying to achieve. My real world project is a simple scripting language that uses a parser, data tree, and interpreter (instead of a VM stack system). I need to use some kind of data structure (perhaps map) to store the variables names created by script programmers. These are likely to be pretty randomly named, so I need a lookup method that can quickly find a particular key within a (probably) fairly large list of names. #include <ctime> #include <map> #include <vector> #include <iostream> struct mystruct { char key; int value; mystruct(char k = 0, int v = 0) : key(k), value(v) { } }; int find(const std::vector<mystruct>& ref, char key) { for (std::vector<mystruct>::const_iterator i = ref.begin(); i != ref.end(); ++i) if (i->key == key) return i->value; return -1; } int main() { std::map<char, int> mymap; std::vector<mystruct> myvec; for (int i = 'a'; i < 'a' + 26; ++i) { mymap[i] = i - 'a'; myvec.push_back(mystruct(i, i - 'a')); } int pre = clock(); for (int i = 0; i < 10000000; ++i) { find(myvec, 'z'); } std::cout << "linear scan: milli " << clock() - pre << "\n"; pre = clock(); for (int i = 0; i < 10000000; ++i) { mymap['z']; } std::cout << "map scan: milli " << clock() - pre << "\n"; return 0; }

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  • Split a Large File In C++

    - by wdow88
    Hey all, I'm trying to write a program that takes a large file (of any time) and splits it into many smaller "chunks". I think I have the basic idea down, but for some reason I cannot create a chunk size over 12,000 bites. I know there are a few solutions on google, etc. but I am more interested in learning what the origin of this limitation is then actually using the program to split files. //This file splits are larger into smaller files of a user inputted size. #include<iostream> #include<fstream> #include<string> #include<sstream> #include <direct.h> #include <stdlib.h> using namespace std; void GetCurrentPath(char* buffer) { _getcwd(buffer, _MAX_PATH); } int main() { // use the function to get the path char CurrentPath[_MAX_PATH]; GetCurrentPath(CurrentPath);//Get the current directory (used for displaying output) fstream bigFile; string filename; int partsize; cout << "Enter a file name: "; cin >> filename; //Recieve target file cout << "Enter the number of bites in each smaller file: "; cin >> partsize; //Recieve volume size bigFile.open(filename.c_str(),ios::in | ios::binary); bigFile.seekg(0, ios::end); // position get-ptr 0 bytes from end int size = bigFile.tellg(); // get-ptr position is now same as file size bigFile.seekg(0, ios::beg); // position get-ptr 0 bytes from beginning for (int i = 0; i <= (size / partsize); i++) { //Build File Name string partname = filename; //The original filename string charnum; //archive number stringstream out; //stringstream object out, used to build the archive name out << "." << i; charnum = out.str(); partname.append(charnum); //put the part name together //Write new file part fstream filePart; filePart.open(partname.c_str(),ios::out | ios::binary); //Open new file with the name built above //Check if near the end of file if (bigFile.tellg() < (size - (size%partsize))) { filePart.write(reinterpret_cast<char *>(&bigFile),partsize); //Write the selected amount to the file filePart.close(); //close file bigFile.seekg(partsize, ios::cur); //move pointer to next position to be written } //Changes the size of the last volume because it is the end of the file else { filePart.write(reinterpret_cast<char *>(&bigFile),(size%partsize)); //Write the selected amount to the file filePart.close(); //close file } cout << "File " << CurrentPath << partname << " produced" << endl; //display the progress of the split } bigFile.close(); cout << "Split Complete." << endl; return 0; } Any ideas? Thanks!

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