线程池实际上也是一个生产者消费者模型，线程池可以让多个线程去任务队列中取任务，执行任务，适用于需要大量的线程来完成任务且完成任务的时间较短。
#include "log.hpp"
#include <mutex>
#include <condition_variable>
#include <queue>
#include <thread>
#include <functional>namespace thread_pool_module
{using namespace log_module;const size_t default_thread_count = 4;//任务类型//约定任务就是线程的回调方法//任务应该是无参无返回值的的调用对象template <class T>class thread_pool{private://只指定线程数量thread_pool(size_t thread_count = default_thread_count):_threads(thread_count),_wait_thread_count(0),_is_running(false){LOG(LOG_LEVEL::INFO) << "thread_pool init";}//拷贝构造函数thread_pool(const thread_pool<T>&) = delete;//赋值构造函数thread_pool<T>& operator=(const thread_pool<T>&) = delete;//线程获取任务void thread_get_task(){//线程一直不停地获取任务while(true) {std::unique_lock<std::mutex> lock(_mutex);while(_task_queue.empty() && _is_running){//等待任务++_wait_thread_count;_condition.wait(lock); --_wait_thread_count;}//线程池停止运行并且任务队列为空if(!_is_running && _task_queue.empty()){return;}//获取任务T& task = _task_queue.front();_task_queue.pop();//执行任务LOG(LOG_LEVEL::INFO) << "thread_get_task, run task" << std::this_thread::get_id();task();} }public:static thread_pool<T> &get_instance(size_t thread_count = default_thread_count){static thread_pool<T> instance(thread_count);return instance;}//启动线程池void start(){ if(_is_running){return;}_is_running = true;LOG(LOG_LEVEL::INFO) << "thread_pool start ";for(std::thread& t : _threads){std::function<void()> f = std::bind(&thread_pool<T>::thread_get_task, this);t = std::thread(f);}}//添加任务void add_task(const T& task){if(!_is_running){ LOG(LOG_LEVEL::ERROR) << "thread_pool is not running";return;}_mutex.lock();_task_queue.push(task);if(_wait_thread_count > 0){_condition.notify_one();}_mutex.unlock();}//等待线程池中的任务执行完毕void wait(){for(std::thread& t : _threads){LOG(LOG_LEVEL::INFO) << "thread_pool wait " << t.get_id();t.join();}}//停止线程池void stop(){if(!_is_running){LOG(LOG_LEVEL::ERROR) << "thread_pool is not running";return;}LOG(LOG_LEVEL::INFO) << "thread_pool stop";_is_running = false;_condition.notify_all();}private:std::vector<std::thread> _threads;std::queue<T> _task_queue;std::mutex _mutex;std::condition_variable _condition; //表示线程池中是否有任务size_t _wait_thread_count; //等待任务的线程数量bool _is_running; //线程池是否在运行};}
)
)
