条件变量实例：生产者-消费者模式的后进先出型(std::stack)缓冲区

综合应用boost::thread库（thread, mutex, condition_variable_any）实现的 生产者-消费者模式
后进先出型(std::stack)缓冲区
stack可以经过轻微修改使用队列替换。

#include <boost/thread.hpp>using namespace boost;#include <stack>#include <iostream>using std::stack;using std::cout;using std::endl;//生产者-消费者模式的后进先出型(std::stack)缓冲区class Buffer{public:    //构造函数    Buffer(size_t n) :un_read(0), capacity(n){}    //写入数据x    void put(int x){        //局部域        {            mutex::scoped_lock lock(mu);  //锁定互斥量            while (is_full()){                cond_put.wait(mu);  //条件变量等待            }            stk.push(x);  //写入数据            ++un_read;        }  //解锁互斥量        cond_get.notify_one();  //通知可以读取数据    }    //读取数据    void get(int *x){        {            mutex::scoped_lock lock(mu);            while (is_empty()){                cond_get.wait(mu);            }            *x = stk.top();            stk.pop();            --un_read;        }        cond_put.notify_one();    }private:    //判断缓冲区是否满    bool is_full(){        return un_read == capacity;    }    //判断缓冲区是否为空    bool is_empty(){        return un_read == 0;    }private:    mutex mu;  //互斥量，配合条件变量使用    condition_variable_any cond_put;  //写入条件变量    condition_variable_any cond_get;  //读取条件变量    stack<int> stk;  //缓冲区对象    int un_read;    int capacity;};Buffer buf(5);  //定义一个缓冲区对象mutex io_mu_;  //定义一个输出互斥量//生产者,n个void producer(int n){    for (int i = 0; i < n; i++){        //输出信息        {            mutex::scoped_lock lock(io_mu_);            cout << "put " << i <<" to buffer"<< endl;        }        buf.put(i);  //写入数据    }}//消费者void consumer(int n){    int result(0);    for (int i = 0; i < n; i++){        {             buf.get(&result);  //读取数据            mutex::scoped_lock lock(io_mu_);            cout << "get " << result << " from buffer" << endl;        }    }}void producer_consumer_test(){    thread t_producer(producer, 20);    thread t_consumer1(consumer, 10);    thread t_consumer2(consumer, 10);    t_producer.join();    t_consumer1.join();    t_consumer2.join();}

运行结果为：