c++多线程（十八） - windows临界区

秒速五厘米 2022-02-05 01:17 251阅读 0赞

### 1. windows临界区 ###

#include<iostream>
    #include<thread>
    #include<list>
    #include<windows.h>
    using namespace std;
    class MsgManage
    {
    public:
    	MsgManage()
    	{
    		InitializeCriticalSection(&myWInsec);//初始化windows临界区
    	}
    	~MsgManage() {}
    	void InMsg()
    	{
    		for (int i = 0; i < 10000; i++)
    		{
    			cout << "插入元素: " << i << endl;
    			EnterCriticalSection(&myWInsec); //进入临界区
    			myList.push_back(i);
    			LeaveCriticalSection(&myWInsec); //离开临界区		
    		}
    	}
    	bool outMsgProc(int &num)
    	{
    		EnterCriticalSection(&myWInsec); //进入临界区
    		if (!myList.empty())
    		{
    			num = myList.front();
    			myList.pop_front();
    			LeaveCriticalSection(&myWInsec); //离开临界区
    			return true;
    		}
    		LeaveCriticalSection(&myWInsec); //离开临界区
    		return false;
    	}
     
    	void OutMsg()
    	{
    		for (int i = 0; i < 10000; i++)
    		{
    			int num;
    			bool result = outMsgProc(num);
    			if (result)
    			{
    				cout << "移除元素: " << num << endl;
    			}
    			else
    			{
    				cout << "消息队列为空" << endl;
    			}
    		}
    	}
    private:
    	list<int> myList;
    	CRITICAL_SECTION myWInsec; //windows临界区
    };
     
    int main()
    {
    	MsgManage manage;
    	thread outMsg(&MsgManage::OutMsg, &manage);
    	thread inMsg(&MsgManage::InMsg, &manage);
    	inMsg.join();
    	outMsg.join();
    	return 0;
    }

### 2.自动析构 ###

EnterCriticalSection()和LeaveCriticalSection()必须成对使用。但是程序员很容易EnterCriticalSection()后忘记调用LeaveCriticalSection()，导致代码段长时间锁定。为了避免这个问题，设计一个资源管理类，在构造函数里调用EnterCriticalSection()，在析构函数里调用LeaveCriticalSection()，程序员再也不用担心资源释放的问题了。这个类的作用类似于c++11中的lock\_guard。

#include<iostream>
    #include<thread>
    #include<list>
    #include<windows.h>
    using namespace std;
    class CWinLock
    {
    public:
    	CWinLock(CRITICAL_SECTION *pCritical)
    	{
    		m_pCritical = pCritical;
    		EnterCriticalSection(m_pCritical); //进入临界区
    	}
    	~CWinLock()
    	{
    		LeaveCriticalSection(m_pCritical); //离开临界区	
    	}
    private:
    	CRITICAL_SECTION *m_pCritical; //windows临界区
    };
    
    class MsgManage
    {
    public:
    	MsgManage()
    	{
    		InitializeCriticalSection(&myWInsec);//初始化windows临界区
    	}
    	~MsgManage() {}
    	void InMsg()
    	{
    		for (int i = 0; i < 10000; i++)
    		{
    			cout << "插入元素: " << i << endl;
    			CWinLock winLock(&myWInsec);
    			myList.push_back(i);		
    		}
    	}
    	bool outMsgProc(int &num)
    	{
    		CWinLock winLock(&myWInsec);
    		if (!myList.empty())
    		{
    			num = myList.front();
    			myList.pop_front();
    			return true;
    		}
    		return false;
    	}
    
    	void OutMsg()
    	{
    		for (int i = 0; i < 10000; i++)
    		{
    			int num;
    			bool result = outMsgProc(num);
    			if (result)
    			{
    				cout << "移除元素: " << num << endl;
    			}
    			else
    			{
    				cout << "消息队列为空" << endl;
    			}
    		}
    	}
    private:
    	list<int> myList;
    	CRITICAL_SECTION myWInsec; //windows临界区
    };
    
    int main()
    {
    	MsgManage manage;
    	thread outMsg(&MsgManage::OutMsg, &manage);
    	thread inMsg(&MsgManage::InMsg, &manage);
    	inMsg.join();
    	outMsg.join();
    	return 0;
    }