muduo库学习笔记九：base库之BlockingQueue

BlockingQueue类：使用条件变量实现的无界队列

类图：

其中：

mutex_：互斥量

notEmpty_：条件变量

queue_：队列

put：生产产品

take:消费产品

size：队列大小

以生产者消费者模型来说明该类的使用：（这里假设队列是有界的，所有生产前需要判断队列是否已满）

测试程序：

#include 
#include 
#include 

#include 
#include 
#include 
#include 

class Test
{
 public:
  Test(int numThreads)
    : latch_(numThreads),//初始化计数值为5
      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));//创建5个线程
  }

  void run(int times)//主线程是生产者，生产10个产品
  {
    printf("waiting for count down latch\n");
    latch_.wait();//等待信号
    printf("all threads started\n");
    for (int i = 0; i < times; ++i)
    {
      char buf[32];
      snprintf(buf, sizeof buf, "hello %d", i);
      queue_.put(buf);//put完后会notify
      printf("tid=%d, put data = %s, size = %zd\n", muduo::CurrentThread::tid(), buf, queue_.size());
    }
  }

  void joinAll()//队列中产生5个stop产品，并且将所有线程都join归并
  {
    for (size_t i = 0; i < threads_.size(); ++i)
    {
      queue_.put("stop");//5个stop产品会被5个线程分别取走
    }

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

 private:

  void threadFunc()//5个子线程是消费者
  {
    printf("tid=%d, %s started\n",
           muduo::CurrentThread::tid(),
           muduo::CurrentThread::name());

    latch_.countDown();//计数值初始为5，每个线程减1，五个线程创建完刚好结束
    bool running = true;
    while (running)
    {
      std::string d(queue_.take());//当queue_为空时，等待...
      printf("tid=%d, get data = %s, size = %zd\n", muduo::CurrentThread::tid(), d.c_str(), queue_.size());
      running = (d != "stop");
    }

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

  muduo::BlockingQueue queue_;
  muduo::CountDownLatch latch_;
  boost::ptr_vector threads_;
};

int main()
{
  printf("pid=%d, tid=%d\n", ::getpid(), muduo::CurrentThread::tid());
  Test t(5);
  t.run(10);
  t.joinAll();

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

执行结果：

BoundedBlockingQueue类（有界缓冲区）：利用boost_circular_buffer实现环形缓冲区，主要方便拷贝

类图：

其中：

mutex：互斥量

notEmpty：条件变量

notFull:条件变量

queue：队列

put：生产产品

take:消费产品

size：当前产品个数

empty()：队列是否为空

full()：队列是否为满

capacity():总容量

使用不做过多的解释。。