注册 登录
编程论坛 VC++/MFC

多线程的为啥不输出“only one”谢谢

renhongjin 发布于 2013-03-25 22:15, 433 次点击
#include<windows.h>
#include<iostream.h>


DWORD WINAPI Fun1Proc(LPVOID lpParameeter);
DWORD WINAPI Fun2Proc(LPVOID lpParameeter);


int tickets=100;
HANDLE g_hEvent;


void main()
{
    HANDLE hThread1;
    HANDLE hThread2;

    g_hEvent=CreateEvent(NULL,FALSE,FALSE,"tickets");
    if(g_hEvent)
    {
        if(ERROR_ALREADY_EXISTS==GetLastError())
        {
            cout<<"only one "<<endl;
            return ;
        }
    }

    SetEvent(g_hEvent);
    hThread1=CreateThread(NULL,0,Fun1Proc,NULL,0,NULL);
    hThread2=CreateThread(NULL,0,Fun2Proc,NULL,0,NULL);

    CloseHandle(hThread1);
    CloseHandle(hThread2);

    Sleep(400);

    CloseHandle(g_hEvent);

}


DWORD WINAPI Fun1Proc(LPVOID lpParameeter)
{
    while(TRUE)
    {
        
        WaitForSingleObject(g_hEvent,INFINITE);//都可以请求
//        ResetEvent(g_hEvent);//都可以请求
        if(tickets>0)
        {
            //Sleep(1);
            cout<<"Thread1 sell ticket:"<<tickets--<<endl;
        }
        else
            break;
        SetEvent(g_hEvent);
    }

    return 0;
}

DWORD WINAPI Fun2Proc(LPVOID lpParameeter)
{
    while(TRUE)
    {
        WaitForSingleObject(g_hEvent,INFINITE);
//        ResetEvent(g_hEvent);
        if(tickets>0)
        {
            //Sleep(1);
            cout<<"Thread2 sell ticket:"<<tickets--<<endl;
        }
        else
            break;
        SetEvent(g_hEvent);
    }

    return 0;
}
1 回复
#2
yuccn2013-03-25 22:23

g_hEvent=CreateEvent(NULL,FALSE,FALSE,"tickets"); // @1
if(g_hEvent)
     {
         if(ERROR_ALREADY_EXISTS==GetLastError())
                                                   
         {
             cout<<"only one "<<endl;
             return ;
         }
     }

// 事件已经被创建了,不是刚刚@1处被创建的,而是被其他程序 创建的,@1也会
// 返回Event,同时设置了LastError 为 ERROR_ALREADY_EXISTS。
// 如果你想有only one输出,那么 启动两个程序,那么第二个程序就能够看到only one了
 
1