用C++和Windows的互斥对象（Mutex）来实现线程同步锁
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;
}