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CountDownLatch的基于对象的客户端用户使用方法

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2020年6月3日 上午8:33

总结：

基于对象的方式，能够将新建线程相关的函数方法、全局变量封装在一个对象中，并且主线程main也可以通过这个类对象和新建线程交互

方式1：新建线程组等待主线程唤醒

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#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;
/*
利用基于对象的编程方式，将主线程和创建的线程组进行逻辑上的分离
*/
class Test
{
public:
  // 第二层新线程组：在构造函数中启动创建线程，并启动
  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));
  }
  // 第二层新线程组：用于主线程中唤醒新线程
  void run()
  {
    latch_.countDown();
  }

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

private:
  // 第二层新线程组:多线程的共同执行体，会发生锁的争抢
  void threadFunc()
  {
    latch_.wait();
    printf("tid=%d, %s started\n",
           CurrentThread::tid(),
           CurrentThread::name());

    printf("tid=%d, %s stopped\n",
           CurrentThread::tid(),
           CurrentThread::name());
  }
  // 第二层新线程组：三个新线程需要的共同的全局变量
  CountDownLatch latch_;
  boost::ptr_vector<Thread> threads_;
};

int main()
{
  printf("pid=%d, tid=%d\n", ::getpid(), CurrentThread::tid());
  // 第一层主线程：启动三个新线程
  Test t(3);
  sleep(3);
  printf("pid=%d, tid=%d %s running ...\n", ::getpid(), CurrentThread::tid(), CurrentThread::name());
  // 第一层主线程：唤醒那三个线程
  t.run();
  t.joinAll();

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

方式2：新建线程组完成功能后将主线程进行唤醒

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#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);
    latch_.countDown();
    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);
  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());
}