A C++ multi thread safe singleton example with source code has been posted

Lock.h

//Example from http://www.relisoft.com/Win32/active.html #if !defined _LOCK_H_ #define _LOCK_H_

#include “Mutex.h”

class Lock { public: // Acquire the state of the semaphore Lock ( Mutex & mutex ) : _mutex(mutex) { _mutex.Acquire(); } // Release the state of the semaphore ~Lock () { _mutex.Release(); } private: Mutex & _mutex; };

#endif

Mutex.h

//Example from http://www.relisoft.com/Win32/active.html #if !defined _MUTEX_H_ #define _MUTEX_H_

class Mutex { friend class Lock; public: Mutex () { InitializeCriticalSection (& _critSection); } ~Mutex () { DeleteCriticalSection (& _critSection); } private: void Acquire () { EnterCriticalSection (& _critSection); } void Release () { LeaveCriticalSection (& _critSection); }

CRITICAL_SECTION _critSection; };

#endif

Singleton.h

#include “Lock.h” #include “Mutex.h”

class aSingletonClass { public: //method to get Instance of class static aSingletonClass *getInstance( void ) { //Note that the class is only created when this method is called first time if(!instance_) instance_ = new aSingletonClass; return instance_; } //method to delete Instance of class static void deleteInstance( void ) { if(instance_) delete instance_; instance_ = NULL; //important as this can create dead reference problems } void printSomething(char *name, int count) { Lock guard(mutex_); std::cout << name << " loop " << count << std::endl; } private: //variable to store the instance of singleton static aSingletonClass *instance_; //default constructor should be private to prevent instantiation aSingletonClass() {}; //destructor should be made private so no one can delete this accidently ~aSingletonClass() {}; //We also need to prevent copy being created of the object aSingletonClass(const aSingletonClass&); Mutex mutex_; }; Thread.cpp //Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy //This shows example of Multithreading, thread sync, Mutex #include #include #include #include “Singleton.h”

using namespace std;

aSingletonClass* aSingletonClass::instance_ = NULL;

void Func1(void *); void Func2(void *);

int main() { HANDLE hThreads[2];

aSingletonClass *someVar = NULL; //Create Instance someVar = aSingletonClass::getInstance();

//Create two threads and start them hThreads[0] = (HANDLE)_beginthread(Func1, 0, NULL); hThreads[1] = (HANDLE)_beginthread(Func2, 0, NULL);

//Makes sure that both the threads have finished before going further WaitForMultipleObjects(2, hThreads, TRUE, INFINITE);

cout << "Main exit" << endl; return 0; } void Func1(void *P) { int Count; for (Count = 1; Count < 11; Count++) { aSingletonClass::getInstance()->printSomething(“Func1”, Count); } return; }

void Func2(void *P) { int Count;

for (Count = 10; Count > 0; Count–) { aSingletonClass::getInstance()->printSomething(“Func2”, Count); } return; }

#Singleton #safe #C #sourcecode #example #multithread