C++ 实现线程安全的任务队列

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C++ 实现线程安全的任务队列

flyfish 2015-3-6

一、三个接口函数说明

1 add 新增任务
2 get_nonblocking 非阻塞获取任务或者空任务
3 get_blocking 阻塞获取任务
头文件

#pragma once#include <deque>#include <boost/thread/mutex.hpp>#include <boost/thread/locks.hpp>#include <boost/thread/condition_variable.hpp>//任务 网络发送任务使用的结构，通常有一个发送缓冲区和一个实际要发送的长度class task{public:unsigned char data[2048];unsigned int len;//实际发送长度task::task();task::~task();};class task_queue{private:std::deque<task> tasks;boost::mutex tasks_mutex;boost::condition_variable cv;public:task_queue::task_queue();task_queue::~task_queue();void add(const task& task);std::tuple<bool,task> get_nonblock();task get_block();};

实现文件

#include "task_queue.h"//tasktask::task(){for (int i=0;i<2048;i++)data[i] = 0;}task::~task(){}// task queuetask_queue::task_queue(){}task_queue::~task_queue(){}void task_queue::add(const task& task){boost::unique_lock<boost::mutex> lock(tasks_mutex);//不允许其他线程执行 tasks.push_back(task);lock.unlock();cv.notify_one();//通知其他线程继续}std::tuple<bool,task> task_queue::get_nonblock(){boost::lock_guard<boost::mutex> lock(tasks_mutex);std::tuple<bool,task> ret;if (!tasks.empty()){ret=std::make_tuple(true,tasks.front());tasks.pop_front();}else{task tmp;ret=std::make_tuple(false,tmp);}return ret;}task task_queue::get_block(){boost::unique_lock<boost::mutex> lock(tasks_mutex);while (tasks.empty()){cv.wait(lock);}task ret=tasks.front();tasks.pop_front();return ret;}

二解释
1 notify_one用于唤醒一个等待该条件(condition)发生的线程
2 可以使用boost::mutex::scoped_lock 替换boost::unique_lock<boost::mutex>，可以避免遗漏unlock
例如

boost::mutex mutex_;try{mutex_.lock();//do somethingmutex_.unlock();}catch(...){mutex_.unlock();return 0;}

使用boost::mutex::scoped_lock就可以避免catch遗漏unlock

3 boost::unique_lock仅仅比boost::lock_guard附加一些功能

4 如果任务在获取之后不删除，就可以使用多读一写方式，就要实现读写锁

读操作发生时：写线程停止操作，允许多个线程同时读操作
写操作发生时：只允许同一时刻只有一个线程写操作，其他无论读写线程全部停止。
代码类似

typedef boost::shared_lock<boost::shared_mutex> r_lock; typedef boost::unique_lock<boost::shared_mutex> w_lock;  boost::shared_mutex mutex_;  void read()  {  r_lock lock(mutex_);  //do something  }  void write()  {  w_lock lock(mutex_);  //do something  }

模板方式

<pre name="code" class="cpp">#pragma once#include <tuple>#include <deque>#include <boost/thread/mutex.hpp>#include <boost/thread/locks.hpp>#include <boost/thread/condition_variable.hpp>template <typename T>class task_queue{private:std::deque<T> tasks;boost::mutex tasks_mutex;boost::condition_variable cv;public:void add(const  T&  t){boost::unique_lock<boost::mutex> lock(tasks_mutex); tasks.push_back(t);lock.unlock();cv.notify_one();}std::tuple<bool, T> get_nonblock(){boost::lock_guard<boost::mutex> lock(tasks_mutex);std::tuple<bool,T> ret;if (!tasks.empty()){ret=std::make_tuple(true,tasks.front());tasks.pop_front();}else{T tmp;ret=std::make_tuple(false,tmp);}return ret;}T get_block(){boost::unique_lock<boost::mutex> lock(tasks_mutex);while (tasks.empty()){cv.wait(lock);}T ret=tasks.front();tasks.pop_front();return ret;}};

以上程序在VC2010 Boost库下编译通过

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