多线程练习----读者写者问题-优快云博客

本文探讨了使用C++并发编程技术实现线程同步与互斥的实例，通过创建线程并实现读写操作，展示了如何确保数据一致性与并发安全。

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#include <windows.h> #include <iostream> #include <process.h> #include <cstdlib> #include <ctime> using namespace std; DWORD WINAPI Reader(LPVOID lpParameter); DWORD WINAPI Writer(LPVOID lpParameter); //全局变量 CRITICAL_SECTION ReaderMutex, WriteMutex;//这个变量用来保证输出时不会竞争 CRITICAL_SECTION WritePrior; int ReaderCount = 0; int main(int argc,char *argv[]) { HANDLE hthread[5]; HANDLE hWriter; int i; int arg[5]; int count = 5; unsigned long retval; InitializeCriticalSection(&WriteMutex); InitializeCriticalSection(&ReaderMutex); InitializeCriticalSection(&WritePrior); for(i = 0; i<5;i++) { arg[i] = i; hthread[i] = CreateThread(NULL, 0, Reader, (void*)(arg+i), 0, NULL); if( hthread[i] == INVALID_HANDLE_VALUE)//如果线程创建失败返回-1 { cerr << "error while create thread " << i <<endl; cerr << "error code : "<< GetLastError() <<endl; } } hWriter = CreateThread(NULL, 0, Writer, NULL, 0, NULL); //等待所有线程结束 retval = WaitForMultipleObjects(5,hthread,true,INFINITE);//等待多个线程 if(retval == WAIT_FAILED) { cerr<< "wait error,error code: "<<GetLastError()<<endl; } for(i = 0; i<5;i++) { if(CloseHandle(hthread[i]) == false)//关闭句柄 { cerr << "error while close thread " <<i<<endl; cerr << "error code: "<<GetLastError()<<endl; } } DeleteCriticalSection( &WriteMutex); DeleteCriticalSection( &ReaderMutex); DeleteCriticalSection( &WritePrior); return 0; } DWORD WINAPI Reader(LPVOID lpParameter) { int n = ((int *)lpParameter)[0]; while(true) { //EnterCriticalSection( &WritePrior); EnterCriticalSection( &ReaderMutex); if ( ReaderCount == 0 )EnterCriticalSection(&WriteMutex); ReaderCount++; LeaveCriticalSection( &ReaderMutex); cout << "Reader " << n << "is reading " << endl; Sleep(15); EnterCriticalSection( &ReaderMutex); ReaderCount--; if ( ReaderCount == 0 )LeaveCriticalSection(&WriteMutex); LeaveCriticalSection( &ReaderMutex); //LeaveCriticalSection( &WritePrior); Sleep(1); } return n; } DWORD WINAPI Writer(LPVOID lpParameter) { while(true) { //EnterCriticalSection( &WritePrior); EnterCriticalSection( &WriteMutex); cout << "Process write. The number of reader:" << ReaderCount<< endl; Sleep(15); LeaveCriticalSection( &WriteMutex); //LeaveCriticalSection( &WritePrior); //Sleep(10); } return 0; }