第9章 用内核对象进行线程同步（3）_信号量(semaphore）、互斥量(mutex)

#include <windows.h>
#include <tchar.h>
#include <locale.h>

//////////////////////////////////////////////////////////////////////////
//一个只能容纳10个客人的餐馆来了12个客户
#define MAX_SEM_COUNT   10
#define THREADCOUNT     12

//////////////////////////////////////////////////////////////////////////
HANDLE  g_hSemaphore = NULL;
DWORD  WINAPI ThreadProc(LPVOID pvParam);

//////////////////////////////////////////////////////////////////////////
int _tmain()
{

    _tsetlocale(LC_ALL, _T("chs"));

    HANDLE aThread[THREADCOUNT] = { NULL };
    DWORD dwThreadID = 0;

    g_hSemaphore = CreateSemaphore(NULL, MAX_SEM_COUNT, MAX_SEM_COUNT, NULL);
    //以下两句与上面那句的实现的效果一样，先创建无资源的信号量，再增加资源
    //g_hSemaphore = CreateSemaphore(NULL, 0, MAX_SEM_COUNT, NULL);
    //ReleaseSemaphore(g_hSemaphore, MAX_SEM_COUNT, NULL);

    if (NULL == g_hSemaphore){
        _tprintf(_T("创建信号量失败:%d\n"), GetLastError());
        return -1;
    }

    //创建12个线程
    for (int i = 0; i < THREADCOUNT;i++){
        aThread[i] = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadProc,
                                NULL,0,&dwThreadID);
        if (aThread[i] == NULL){
            _tprintf(_T("创建线程失败:%d\n"), GetLastError());
            return -1;    
        }
    }

    //等待所有线程结束
    WaitForMultipleObjects(THREADCOUNT, aThread, TRUE, INFINITE);

    //关闭所有子线程
    for (int i = 0; i < THREADCOUNT;i++){
        CloseHandle(aThread[i]);
    }

    //关闭信号量
    CloseHandle(g_hSemaphore);

    _tsystem(_T("PAUSE"));
    return 0;
}

//线程函数
DWORD  WINAPI ThreadProc(LPVOID pvParam)
{
    DWORD  dwWaitResult;
    BOOL bContinue = TRUE;
    LONG lPrevCount=0;

    while (bContinue){
        //等待资源，立即返回
        dwWaitResult = WaitForSingleObject(g_hSemaphore, 0L);
        switch (dwWaitResult)
        {
        case WAIT_OBJECT_0:
            bContinue = FALSE;
            _tprintf(_T("线程%d:等待成功！\n"), GetCurrentThreadId());

            Sleep(20);

            if (!ReleaseSemaphore(g_hSemaphore, 1, &lPrevCount)){
                _tprintf(_T("ReleaseSemaphore失败:%d！\n"), GetLastError());
            }    

            //_tprintf(_T("线程%d:等待成功，当前可用资源%d！\n"), GetCurrentThreadId(),lPrevCount+1);
            
            break;
        case WAIT_TIMEOUT:
            _tprintf(_T("线程%d:等待超时！\n"), GetCurrentThreadId());
            break;
        }
    }
    _tprintf(_T("线程%d:退出\n"), GetCurrentThreadId());
    return 0;
}