用C++和Windows的互斥对象（Mutex）来实现线程同步锁

//这是2个线程模拟卖火车票的小程序
#include <windows.h>
#include <iostream.h>

DWORD WINAPI Fun1Proc(LPVOID lpParameter);//thread data
DWORD WINAPI Fun2Proc(LPVOID lpParameter);//thread data

int index=0;
int tickets=10;
HANDLE hMutex;
void main()
{
    HANDLE hThread1;
    HANDLE hThread2;
    //创建线程

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

    //创建互斥对象
    hMutex=CreateMutex(NULL,TRUE,"tickets");
    if (hMutex)
    {
        if (ERROR_ALREADY_EXISTS==GetLastError())
        {
            cout<<"only one instance can run!"<<endl;
            return;
        }
    }
    WaitForSingleObject(hMutex,INFINITE);
    ReleaseMutex(hMutex);
    ReleaseMutex(hMutex);
    
    Sleep(4000);
}
//线程1的入口函数
DWORD WINAPI Fun1Proc(LPVOID lpParameter)//thread data
{
    while (true)
    {
        ReleaseMutex(hMutex);
        WaitForSingleObject(hMutex,INFINITE);
        if (tickets>0)
        {
            Sleep(1);
            cout<<"thread1 sell ticket :"<<tickets--<<endl;
        }
        else
            break;
        ReleaseMutex(hMutex);
    }

    return 0;
}
//线程2的入口函数
DWORD WINAPI Fun2Proc(LPVOID lpParameter)//thread data
{
    while (true)
    {
        ReleaseMutex(hMutex);
        WaitForSingleObject(hMutex,INFINITE);
        if (tickets>0)
        {
            Sleep(1);
            cout<<"thread2 sell ticket :"<<tickets--<<endl;
        }
        else
            break;
        ReleaseMutex(hMutex);
    }
    
    return 0;
}

//上面的例子是基于互斥对象的，这个是基于事件对象的
#include <windows.h>
#include <iostream.h>

DWORD WINAPI Fun1Proc(LPVOID lpParameter);//thread data
DWORD WINAPI Fun2Proc(LPVOID lpParameter);//thread data

int tickets=100;
HANDLE g_hEvent;
void main()
{
    HANDLE hThread1;
    HANDLE hThread2;
    //创建人工重置事件内核对象
    g_hEvent=CreateEvent(NULL,FALSE,FALSE,"tickets");
    if (g_hEvent)
    {
        if (ERROR_ALREADY_EXISTS==GetLastError())
        {
            cout<<"only one instance can run!"<<endl;
            return;
        }
    }
    SetEvent(g_hEvent);

    //创建线程
    hThread1=CreateThread(NULL,0,Fun1Proc,NULL,0,NULL);
    hThread2=CreateThread(NULL,0,Fun2Proc,NULL,0,NULL);
    CloseHandle(hThread1);
    CloseHandle(hThread2);
    
    //让主线程睡眠4秒
    Sleep(4000);
    //关闭事件对象句柄
    CloseHandle(g_hEvent);
}
//线程1的入口函数
DWORD WINAPI Fun1Proc(LPVOID lpParameter)//thread data
{
    while (true)
    {
        WaitForSingleObject(g_hEvent,INFINITE);
        //ResetEvent(g_hEvent);
        if (tickets>0)
        {
            Sleep(1);
            cout<<"thread1 sell ticket :"<<tickets--<<endl;
            SetEvent(g_hEvent);
        }
        else
        {
            SetEvent(g_hEvent);
            break;
        }
    }
    
    return 0;
}
//线程2的入口函数
DWORD WINAPI Fun2Proc(LPVOID lpParameter)//thread data
{
    while (true)
    {
        //请求事件对象
        WaitForSingleObject(g_hEvent,INFINITE);
        //ResetEvent(g_hEvent);
        if (tickets>0)
        {
            Sleep(1);
            cout<<"thread2 sell ticket :"<<tickets--<<endl;
            SetEvent(g_hEvent);
        }
        else
        {
            SetEvent(g_hEvent);
            break;
        }
    }

    return 0;
}

 

 

准备知识：1，内核对象互斥体（Mutex）的工作机理，WaitForSingleObject函数的用法，这些可以从MSDN获取详情；2，当两个或 更多线程需要同时访问一个共享资源时，系统需要使用同步机制来确保一次只有一个线程使用该资源。Mutex 是同步基元，它只向一个线程授予对共享资源的独占访问权。如果一个线程获取了互斥体，则要获取该互斥体的第二个线程将被挂起，直到第一个线程释放该互斥体。

下边是我参考开源项目C++ Sockets的代码，写的线程锁类

Lock.h

#ifndef _Lock_H
#define _Lock_H

#include <windows.h>

//锁接口类
class IMyLock
{
public :
   virtual ~IMyLock() {}

   virtual void Lock() const = 0;
   virtual void Unlock() const = 0;
};

//互斥对象锁类
class Mutex : public IMyLock
{
public :
   Mutex();
   ~Mutex();

   virtual void Lock() const ;
   virtual void Unlock() const ;

private :
   HANDLE m_mutex;
};

//锁
class CLock
{
public :
   CLock( const IMyLock&);
   ~CLock();

private :
   const IMyLock& m_lock;
};

#endif

Lock.cpp

#include "Lock.h"

//创建一个匿名互斥对象
Mutex::Mutex()
{
   m_mutex = ::CreateMutex(NULL, FALSE, NULL);
}

//销毁互斥对象，释放资源
Mutex::~Mutex()
{
   ::CloseHandle(m_mutex);
}

//确保拥有互斥对象的线程对被保护资源的独自访问
void Mutex::Lock() const
{
   DWORD d = WaitForSingleObject(m_mutex, INFINITE);
}

//释放当前线程拥有的互斥对象，以使其它线程可以拥有互斥对象，对被保护资源进行访问
void Mutex::Unlock() const
{
   ::ReleaseMutex(m_mutex);
}

//利用C++特性，进行自动加锁
CLock::CLock( const IMyLock& m) : m_lock(m)
{
   m_lock.Lock();
}

//利用C++特性，进行自动解锁
CLock::~CLock()
{
   m_lock.Unlock();
}

下边是测试代码MyLock.cpp

// MyLock.cpp : 定义控制台应用程序的入口点。
//

#include <iostream>
#include <process.h>
#include "Lock.h"

using namespace std;

//创建一个互斥对象
Mutex g_Lock;

//线程函数
unsigned int __stdcall StartThread( void *pParam)
{
   char *pMsg = ( char *)pParam;
   if (!pMsg)
   {
       return (unsigned int )1;
   }

   //对被保护资源（以下打印语句）自动加锁
   //线程函数结束前，自动解锁
   CLock lock(g_Lock);

   for ( int i = 0; i < 5; i++ )
   {
       cout << pMsg << endl;
       Sleep( 500 );
   }

   return (unsigned int )0;
}

int main( int argc, char * argv[])
{
   HANDLE hThread1, hThread2;
   unsigned int uiThreadId1, uiThreadId2;

   char *pMsg1 = "First print thread." ;
   char *pMsg2 = "Second print thread." ;

   //创建两个工作线程，分别打印不同的消息
   //hThread1 = ::CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)StartThread, (void *)pMsg1, 0, (LPDWORD)&uiThreadId1);
   //hThread2 = ::CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)StartThread, (void *)pMsg2, 0, (LPDWORD)&uiThreadId2);

   hThread1 = ( HANDLE )_beginthreadex(NULL, 0, &StartThread, ( void *)pMsg1, 0, &uiThreadId1);
   hThread2 = ( HANDLE )_beginthreadex(NULL, 0, &StartThread, ( void *)pMsg2, 0, &uiThreadId2);

   //等待线程结束
   DWORD dwRet = WaitForSingleObject(hThread1,INFINITE);
   if ( dwRet == WAIT_TIMEOUT )
   {
       TerminateThread(hThread1,0);
   }
   dwRet = WaitForSingleObject(hThread2,INFINITE);
   if ( dwRet == WAIT_TIMEOUT )
   {
       TerminateThread(hThread2,0);
   }

   //关闭线程句柄，释放资源
   ::CloseHandle(hThread1);
   ::CloseHandle(hThread2);

   system ( "pause" );
   return 0;
}

一个实用的mutex类，可以直接应用与工程

#include "mutex.h" 02   03 namespace ZFPT 04 { 05     CMutex::CMutex() 06     { 07         pthread_mutex_init(&m_Mutex, NULL); 08     } 09   10     CMutex::~CMutex() 11     { 12         pthread_mutex_destroy(&m_Mutex); 13     } 14   15     intCMutex::lock() 16     { 17         returnpthread_mutex_lock(&m_Mutex); 18     } 19   20     intCMutex::tryLock() 21     { 22         returnpthread_mutex_trylock(&m_Mutex); 23     } 24   25     intCMutex::unLock() 26     { 27         returnpthread_mutex_unlock(&m_Mutex); 28     } 29   30     CScopeLock::CScopeLock(CMutex& cMutex,bool IsTry): m_Mutex(cMutex) 31     { 32         if(IsTry) 33         { 34             m_Mutex.tryLock(); 35         } 36         else 37         { 38             m_Mutex.lock(); 39         } 40     } 41   42     CScopeLock::~CScopeLock() 43     { 44         m_Mutex.unLock(); 45     } 46   47   48   49 }
02
03 namespace ZFPT
04 {
05     CMutex::CMutex()
06     {
07         pthread_mutex_init(&m_Mutex, NULL);
08     }
09
10     CMutex::~CMutex()
11     {
12         pthread_mutex_destroy(&m_Mutex);
13     }
14
15     intCMutex::lock()
16     {
17         returnpthread_mutex_lock(&m_Mutex);
18     }
19
20     intCMutex::tryLock()
21     {
22         returnpthread_mutex_trylock(&m_Mutex);
23     }
24
25     intCMutex::unLock()
26     {
27         returnpthread_mutex_unlock(&m_Mutex);
28     }
29
30     CScopeLock::CScopeLock(CMutex& cMutex,bool IsTry): m_Mutex(cMutex)
31     {
32         if(IsTry)
33         {
34             m_Mutex.tryLock();
35         }
36         else
37         {
38             m_Mutex.lock();
39         }
40     }
41
42     CScopeLock::~CScopeLock()
43     {
44         m_Mutex.unLock();
45     }
46
47
48
49 }