社区首页 >专栏 >muduo网络库学习之MutexLock类、MutexLockGuard类、Condition类、CountDownLatch类封装中的知识点

muduo网络库学习之MutexLock类、MutexLockGuard类、Condition类、CountDownLatch类封装中的知识点

s1mba

发布于 2017-12-28 04:22:55

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代码可运行

文章被收录于专栏：开发与安全开发与安全

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代码可运行

一、MutexLock 类

class MutexLock : boost::noncopyable

二、MutexLockGuard类

class MutexLockGuard : boost::noncopyable

三、Condition类

class Condition : boost::noncopyable

某个线程：

加锁

while (条件)

wait(); //1、解锁；2、等待通知；3、得到通知返回前重新加锁

解锁

另一个线程：

加锁

更改条件

通知notify（可以移到锁外）

解锁

四、CountDownLatch类

class CountDownLatch : boost::noncopyable

既可以用于所有子线程等待主线程发起 “起跑” 也可以用于主线程等待子线程初始化完毕才开始工作

下面写两个程序测试一下CountDownLatch 的作用：

CountDownLatch_test1:

#include <muduo/base/CountDownLatch.h>
#include <muduo/base/Thread.h>

#include <boost/bind.hpp>
#include <boost/ptr_container/ptr_vector.hpp>
#include <string>
#include <stdio.h>

using namespace muduo;

class Test
{
public:
    Test(int numThreads)
        : latch_(1),
          threads_(numThreads)
    {
        for (int i = 0; i < numThreads; ++i)
        {
            char name[32];
            snprintf(name, sizeof name, "work thread %d", i);
            threads_.push_back(new muduo::Thread(
                                   boost::bind(&Test::threadFunc, this), muduo::string(name)));
        }
        for_each(threads_.begin(), threads_.end(), boost::bind(&Thread::start, _1));
    }

    void run()
    {
        latch_.countDown();
    }

    void joinAll()
    {
        for_each(threads_.begin(), threads_.end(), boost::bind(&Thread::join, _1));
    }

private:

    void threadFunc()
    {
        latch_.wait();
        printf("tid=%d, %s started\n",
               CurrentThread::tid(),
               CurrentThread::name());



        printf("tid=%d, %s stopped\n",
               CurrentThread::tid(),
               CurrentThread::name());
    }

    CountDownLatch latch_;
    boost::ptr_vector<Thread> threads_;
};

int main()
{
    printf("pid=%d, tid=%d\n", ::getpid(), CurrentThread::tid());
    Test t(3);
    sleep(3);
    printf("pid=%d, tid=%d %s running ...\n", ::getpid(), CurrentThread::tid(), CurrentThread::name());
    t.run();
    t.joinAll();

    printf("number of created threads %d\n", Thread::numCreated());
}

执行结果如下：

simba@ubuntu:~/Documents/build/debug/bin$ ./countdownlatch_test1 pid=2994, tid=2994 pid=2994, tid=2994 main running ... tid=2997, work thread 2 started tid=2997, work thread 2 stopped tid=2996, work thread 1 started tid=2996, work thread 1 stopped tid=2995, work thread 0 started tid=2995, work thread 0 stopped number of created threads 3 simba@ubuntu:~/Documents/build/debug/bin$

可以看到其他三个线程一直等到主线程睡眠完执行run()，在里面执行latch_.countDown() 将计数减为0，进而执行notifyall 唤醒后，才开始执行下来。

CountDownLatch_test2:

#include <muduo/base/CountDownLatch.h>
#include <muduo/base/Thread.h>

#include <boost/bind.hpp>
#include <boost/ptr_container/ptr_vector.hpp>
#include <string>
#include <stdio.h>

using namespace muduo;

class Test
{
public:
    Test(int numThreads)
        : latch_(numThreads),
          threads_(numThreads)
    {
        for (int i = 0; i < numThreads; ++i)
        {
            char name[32];
            snprintf(name, sizeof name, "work thread %d", i);
            threads_.push_back(new muduo::Thread(
                                   boost::bind(&Test::threadFunc, this), muduo::string(name)));
        }
        for_each(threads_.begin(), threads_.end(), boost::bind(&muduo::Thread::start, _1));
    }

    void wait()
    {
        latch_.wait();
    }

    void joinAll()
    {
        for_each(threads_.begin(), threads_.end(), boost::bind(&Thread::join, _1));
    }

private:

    void threadFunc()
    {
        sleep(3);
       printf("tid=%d, %s started\n",
               CurrentThread::tid(),
               CurrentThread::name());

        latch_.countDown();
     

        printf("tid=%d, %s stopped\n",
               CurrentThread::tid(),
               CurrentThread::name());
    }

    CountDownLatch latch_;
    boost::ptr_vector<Thread> threads_;
};

int main()
{
    printf("pid=%d, tid=%d\n", ::getpid(), CurrentThread::tid());
    Test t(3);
    t.wait();
    printf("pid=%d, tid=%d %s running ...\n", ::getpid(), CurrentThread::tid(), CurrentThread::name());
    t.joinAll();

    printf("number of created threads %d\n", Thread::numCreated());
}

执行结果输出如下：

simba@ubuntu:~/Documents/build/debug/bin$ ./countdownlatch_test2 pid=4488, tid=4488 tid=4491, work thread 2 started tid=4491, work thread 2 stopped tid=4490, work thread 1 started tid=4490, work thread 1 stopped tid=4489, work thread 0 started pid=4488, tid=4488 main running ... tid=4489, work thread 0 stopped number of created threads 3

可以看出当其他三个线程都启动后，各自执行一次 latch_.countDown()，主线程wait() 返回继续执行下去。

参考：

muduo manual.pdf

《linux 多线程服务器编程：使用muduo c++网络库》

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原始发表：2013-10-31 ，如有侵权请联系 cloudcommunity@tencent.com 删除

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