Mutex互斥器

/************************************************************************
** Mutex 互斥器
** 学习Mutex和WaitForSingleObject一起使用的方法
** 
** 主要函数：
** CreateMutex
** OpenMutex
** ReleaseMutex

** Mutex可以跨进程使用，用途之一防多开
************************************************************************/

#include <iostream>
#include <windows.h>
#include <process.h>

using namespace std;
int a[ 5 ];

const int LOOP_COUNT = 10;
const char * szMutexName = "62634453-F10D-4777-8EE6-C7D1E6325BCF";

UINT __stdcall Thread( void* pParams )
{ 
    int i, num = 1;
    HANDLE hThreadMutex = NULL;

    hThreadMutex = OpenMutex( MUTEX_ALL_ACCESS, FALSE, szMutexName );
    if ( NULL == hThreadMutex )
    {
        return 0;
    }

    for ( int k = 0; k < LOOP_COUNT; ++k )
    {
        cout << "***** thread is blocking *****\n";
        WaitForSingleObject( hThreadMutex, INFINITE );
        for ( i = 0; i < 5; i++ ) a[ i ] = num;
        cout << "***** thread working *****\n";

        if ( k == LOOP_COUNT/2 )
        {
            ExitThread(0);
        }

        ReleaseMutex( hThreadMutex );
        num++;
    }

    return 0;
}

int main( void )
{
    HANDLE hMutex = CreateMutex( NULL, FALSE, szMutexName );
    if ( NULL == hMutex || ERROR_ALREADY_EXISTS == ::GetLastError() )
    {
        cout << "application is already exists!" << endl;   //好奇怪，这样为什么不行呢？
        return 0;
    }

    UINT threadID = 0;
    HANDLE hHandle = (HANDLE)_beginthreadex( NULL, 0, Thread, NULL, 0, &threadID );

    for ( int k = 0; k < LOOP_COUNT; ++k )
    {
        DWORD dwResult = WaitForSingleObject( hMutex, INFINITE );
        switch ( dwResult )
        {
        case WAIT_OBJECT_0:
            {
                cout << "***** main working *****\n";
                for ( int i = 0; i < 5; ++i )
                {
                    cout << a[i] << " ";
                }
                cout << endl;
                ReleaseMutex( hMutex );
            }
            break;
        case WAIT_ABANDONED:
            {
                // 另一线程抛弃了它
                cout << "***** ABANDONED *****\n";
                ReleaseMutex( hMutex );
            }
            break;
        default:
            {
                cout << dwResult << endl;
            }
            break;
        }
    }

    return 0;
}