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

本文主要是介绍muduo网络库学习之MutexLock类、MutexLockGuard类、Condition类、CountDownLatch类封装中的知识点，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

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:

C++ Code  

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71

#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:

C++ Code  

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》

这篇关于muduo网络库学习之MutexLock类、MutexLockGuard类、Condition类、CountDownLatch类封装中的知识点的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！