Semaphore信号量

/************************************************************************ ** Semaphore 信号量 ** 可以将Mutex看作Semaphore的简化版，Mutex锁住的是一份资源， ** Semaphore锁住的是多份资源，可以让多个线程在“同一时间同时运行” ** ** 主要函数： ** CreateSemaphore ** ReleaseSemaphore ** VS2008 MSND的例子 ** ms-help://MS.MSDNQTR.v90.en/dllproc/base/createsemaphore.htm ************************************************************************/ #include <windows.h> #include <stdio.h> #define MAX_SEM_COUNT 5 #define THREADCOUNT 8 HANDLE ghSemaphore; DWORD WINAPI ThreadProc( LPVOID ); void main() { HANDLE aThread[THREADCOUNT]; DWORD ThreadID; int i; // Create a semaphore with initial and max counts of MAX_SEM_COUNT ghSemaphore = CreateSemaphore( NULL, // default security attributes MAX_SEM_COUNT, // initial count // 数目为1，就很像Mutex MAX_SEM_COUNT, // maximum count NULL); // unnamed semaphore if (ghSemaphore == NULL) { printf("CreateSemaphore error: %d\n", GetLastError()); return; } // Create worker threads for( i=0; i < THREADCOUNT; i++ ) { aThread[i] = CreateThread( NULL, // default security attributes 0, // default stack size (LPTHREAD_START_ROUTINE) ThreadProc, NULL, // no thread function arguments 0, // default creation flags &ThreadID); // receive thread identifier if( aThread[i] == NULL ) { printf("CreateThread error: %d\n", GetLastError()); return; } } // Wait for all threads to terminate WaitForMultipleObjects(THREADCOUNT, aThread, TRUE, INFINITE); // Close thread and semaphore handles for( i=0; i < THREADCOUNT; i++ ) CloseHandle(aThread[i]); CloseHandle(ghSemaphore); } DWORD WINAPI ThreadProc( LPVOID lpParam ) { DWORD dwWaitResult; BOOL bContinue=TRUE; while(bContinue) { // Try to enter the semaphore gate. dwWaitResult = WaitForSingleObject( ghSemaphore, // handle to semaphore 0L); // zero-second time-out interval switch (dwWaitResult) { // The semaphore object was signaled. case WAIT_OBJECT_0: // TODO: Perform task printf("***** Thread %d: wait succeeded ******\n", GetCurrentThreadId()); bContinue=FALSE; // Simulate thread spending time on task Sleep(1); // Relase the semaphore when task is finished if (!ReleaseSemaphore( ghSemaphore, // handle to semaphore 1, // increase count by one NULL) ) // not interested in previous count { printf("ReleaseSemaphore error: %d\n", GetLastError()); } break; // The semaphore was nonsignaled, so a time-out occurred. case WAIT_TIMEOUT: printf("Thread %d: wait timed out\n", GetCurrentThreadId()); break; } } return TRUE; }

 

转载于:https://www.cnblogs.com/c007136/archive/2012/08/17/2643554.html