信号量

 

https://blog.csdn.net/sinat_31608641/article/details/106899946

// 信号量.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。
//
 
#include <iostream>
#include <Windows.h>
#include <tchar.h>
 
const TCHAR* szSemaphoreA = _T("_SemaphoreA_");
const TCHAR* szSemaphoreB = _T("_SemaphoreB_");
const TCHAR* szSemaphoreC = _T("_SemaphoreC_");
 
DWORD WINAPI Thread_1(LPVOID param);
DWORD WINAPI Thread_2(LPVOID param);
DWORD WINAPI Thread_3(LPVOID param);
 
HANDLE hSM_1;
HANDLE hSM_2;
HANDLE hSM_3;
 
HANDLE hThread_1;
HANDLE hThread_2;
HANDLE hThread_3;
 
int main()
{
 
    // 创建三个信号量
 
    hSM_1 = CreateSemaphore(NULL, 1, 1, szSemaphoreA);//开始为signal状态
    hSM_2 = CreateSemaphore(NULL, 0, 1, szSemaphoreB);//开始为unsignal状态，等待hSM_1释放
    hSM_3 = CreateSemaphore(NULL, 0, 1, szSemaphoreC);//开始为unsignal状态，等待hSM_2
 
    //创建三个线程
 
    hThread_1 = CreateThread(NULL, 0, Thread_1, NULL, 0, NULL);
    hThread_2 = CreateThread(NULL, 0, Thread_2, NULL, 0, NULL);
    hThread_3 = CreateThread(NULL, 0, Thread_3, NULL, 0, NULL);
 
    //等待三个线程都执行完
    WaitForSingleObject(hThread_1, INFINITE);
    WaitForSingleObject(hThread_2, INFINITE);
    WaitForSingleObject(hThread_3, INFINITE);
 
    //三个线程都执行完
    printf("\n\n\t main end \n");
 
    //关闭句柄
    CloseHandle(hThread_1);
    CloseHandle(hThread_2);
    CloseHandle(hThread_3);
    CloseHandle(hSM_1);
    CloseHandle(hSM_2);
    CloseHandle(hSM_3);
    return 0;
}
 
DWORD WINAPI Thread_1(LPVOID param)
{
    for (int i = 0; i < 10; i++)
    {
        DWORD dwWait = WaitForSingleObject(hSM_1, INFINITE);
 
        //每一个wait过后信号量的数量自动减1，这样就达到了控制同步
 
        printf("A");
        ReleaseSemaphore(hSM_2, 1, NULL);
    }
    return 0;
}
 
DWORD WINAPI Thread_2(LPVOID param)
{
    for (int i = 0; i < 10; i++)
    {
        WaitForSingleObject(hSM_2, INFINITE);
        printf("B");
        ReleaseSemaphore(hSM_3, 1, NULL);
    }
    return 0;
}
 
DWORD WINAPI Thread_3(LPVOID param)
{
    for (int i = 0; i < 10; i++)
    {
        WaitForSingleObject(hSM_3, INFINITE);
        printf("C ");
        ReleaseSemaphore(hSM_1, 1, NULL);
    }
 
    system("pause");
    return 0;
}