C++线程池的实现
在https://www.cnblogs.com/LaiY9/p/14725352.html已经实现了 C 语言版的线程池，如果我们也学过 C++ 的话，可以将其改为 C++ 版本，这样代码不管是从使用还是从感观上都会更简洁一些。
1. 任务队列
1.1 类声明
// 定义任务结构体
using callback = void(*)(void*);
struct Task
{
Task()
{
function = nullptr;
arg = nullptr;
}
Task(callback f, void* arg)
{
function = f;
this->arg = arg;
}
callback function;
void* arg;
};
// 任务队列
class TaskQueue
{
public:
TaskQueue();
~TaskQueue();
// 添加任务
void addTask(Task& task);
void addTask(callback func, void* arg);
// 取出一个任务
Task takeTask();
// 获取当前队列中任务个数
inline int taskNumber()
{
return m_queue.size();
}
private:
pthread_mutex_t m_mutex; // 互斥锁
std::queue<Task> m_queue; // 任务队列
};
其中 Task 是任务类，里边有两个成员，分别是两个指针 void(*)(void*) 和 void*
另外一个类 TaskQueue 是任务队列，提供了添加任务、取出任务、存储任务、获取任务个数、线程同步的功能。
1.2 类定义
TaskQueue::TaskQueue()
{
pthread_mutex_init(&m_mutex, NULL);
}
TaskQueue::~TaskQueue()
{
pthread_mutex_destroy(&m_mutex);
}
void TaskQueue::addTask(Task& task)
{
pthread_mutex_lock(&m_mutex);
m_queue.push(task);
pthread_mutex_unlock(&m_mutex);
}
void TaskQueue::addTask(callback func, void* arg)
{
pthread_mutex_lock(&m_mutex);
Task task;
task.function = func;
task.arg = arg;
m_queue.push(task);
pthread_mutex_unlock(&m_mutex);
}
Task TaskQueue::takeTask()
{
Task t;
pthread_mutex_lock(&m_mutex);
if (m_queue.size() > 0)
{
t = m_queue.front();
m_queue.pop();
}
pthread_mutex_unlock(&m_mutex);
return t;
}
2. 线程池
2.1 类声明
class ThreadPool
{
public:
ThreadPool(int min, int max);
~ThreadPool();
// 添加任务
void addTask(Task task);
// 获取忙线程的个数
int getBusyNumber();
// 获取活着的线程个数
int getAliveNumber();
private:
// 工作的线程的任务函数
static void* worker(void* arg);
// 管理者线程的任务函数
static void* manager(void* arg);
void threadExit();
private:
pthread_mutex_t m_lock;
pthread_cond_t m_notEmpty;
pthread_t* m_threadIDs;
pthread_t m_managerID;
TaskQueue* m_taskQ;
int m_minNum;
int m_maxNum;
int m_busyNum;
int m_aliveNum;
int m_exitNum;
bool m_shutdown = false;
};
2.2 类定义
ThreadPool::ThreadPool(int minNum, int maxNum)
{
// 实例化任务队列
m_taskQ = new TaskQueue;
do {
// 初始化线程池
m_minNum = minNum;
m_maxNum = maxNum;
m_busyNum = 0;
m_aliveNum = minNum;
// 根据线程的最大上限给线程数组分配内存
m_threadIDs = new pthread_t[maxNum];
if (m_threadIDs == nullptr)
{
cout << "malloc thread_t[] 失败...." << endl;;
break;
}
// 初始化
memset(m_threadIDs, 0, sizeof(pthread_t) * maxNum);
// 初始化互斥锁,条件变量
if (pthread_mutex_init(&m_lock, NULL) != 0 ||
pthread_cond_init(&m_notEmpty, NULL) != 0)
{
cout << "init mutex or condition fail..." << endl;
break;
}
/////////////////// 创建线程 //////////////////
// 根据最小线程个数, 创建线程
for (int i = 0; i < minNum; ++i)
{
pthread_create(&m_threadIDs[i], NULL, worker, this);
cout << "创建子线程, ID: " << to_string(m_threadIDs[i]) << endl;
}
// 创建管理者线程, 1个
pthread_create(&m_managerID, NULL, manager, this);
} while (0);
}
ThreadPool::~ThreadPool()
{
m_shutdown = 1;
// 销毁管理者线程
pthread_join(m_managerID, NULL);
// 唤醒所有消费者线程
for (int i = 0; i < m_aliveNum; ++i)
{
pthread_cond_signal(&m_notEmpty);
}
if (m_taskQ) delete m_taskQ;
if (m_threadIDs) delete[]m_threadIDs;
pthread_mutex_destroy(&m_lock);
pthread_cond_destroy(&m_notEmpty);
}
void ThreadPool::addTask(Task task)
{
if (m_shutdown)
{
return;
}
// 添加任务，不需要加锁，任务队列中有锁
m_taskQ->addTask(task);
// 唤醒工作的线程
pthread_cond_signal(&m_notEmpty);
}
int ThreadPool::getAliveNumber()
{
int threadNum = 0;
pthread_mutex_lock(&m_lock);
threadNum = m_aliveNum;
pthread_mutex_unlock(&m_lock);
return threadNum;
}
int ThreadPool::getBusyNumber()
{
int busyNum = 0;
pthread_mutex_lock(&m_lock);
busyNum = m_busyNum;
pthread_mutex_unlock(&m_lock);
return busyNum;
}
// 工作线程任务函数
void* ThreadPool::worker(void* arg)
{
ThreadPool* pool = static_cast<ThreadPool*>(arg);
// 一直不停的工作
while (true)
{
// 访问任务队列(共享资源)加锁
pthread_mutex_lock(&pool->m_lock);
// 判断任务队列是否为空, 如果为空工作线程阻塞
while (pool->m_taskQ->taskNumber() == 0 && !pool->m_shutdown)
{
cout << "thread " << to_string(pthread_self()) << " waiting..." << endl;
// 阻塞线程
pthread_cond_wait(&pool->m_notEmpty, &pool->m_lock);
// 解除阻塞之后, 判断是否要销毁线程
if (pool->m_exitNum > 0)
{
pool->m_exitNum--;
if (pool->m_aliveNum > pool->m_minNum)
{
pool->m_aliveNum--;
pthread_mutex_unlock(&pool->m_lock);
pool->threadExit();
}
}
}
// 判断线程池是否被关闭了
if (pool->m_shutdown)
{
pthread_mutex_unlock(&pool->m_lock);
pool->threadExit();
}
// 从任务队列中取出一个任务
Task task = pool->m_taskQ->takeTask();
// 工作的线程+1
pool->m_busyNum++;
// 线程池解锁
pthread_mutex_unlock(&pool->m_lock);
// 执行任务
cout << "thread " << to_string(pthread_self()) << " start working..." << endl;
task.function(task.arg);
delete task.arg;
task.arg = nullptr;
// 任务处理结束
cout << "thread " << to_string(pthread_self()) << " end working...";
pthread_mutex_lock(&pool->m_lock);
pool->m_busyNum--;
pthread_mutex_unlock(&pool->m_lock);
}
return nullptr;
}
// 管理者线程任务函数
void* ThreadPool::manager(void* arg)
{
ThreadPool* pool = static_cast<ThreadPool*>(arg);
// 如果线程池没有关闭, 就一直检测
while (!pool->m_shutdown)
{
// 每隔5s检测一次
sleep(5);
// 取出线程池中的任务数和线程数量
// 取出工作的线程池数量
pthread_mutex_lock(&pool->m_lock);
int queueSize = pool->m_taskQ->taskNumber();
int liveNum = pool->m_aliveNum;
int busyNum = pool->m_busyNum;
pthread_mutex_unlock(&pool->m_lock);
// 创建线程
const int NUMBER = 2;
// 当前任务个数>存活的线程数 && 存活的线程数<最大线程个数
if (queueSize > liveNum && liveNum < pool->m_maxNum)
{
// 线程池加锁
pthread_mutex_lock(&pool->m_lock);
int num = 0;
for (int i = 0; i < pool->m_maxNum && num < NUMBER
&& pool->m_aliveNum < pool->m_maxNum; ++i)
{
if (pool->m_threadIDs[i] == 0)
{
pthread_create(&pool->m_threadIDs[i], NULL, worker, pool);
num++;
pool->m_aliveNum++;
}
}
pthread_mutex_unlock(&pool->m_lock);
}
// 销毁多余的线程
// 忙线程*2 < 存活的线程数目 && 存活的线程数 > 最小线程数量
if (busyNum * 2 < liveNum && liveNum > pool->m_minNum)
{
pthread_mutex_lock(&pool->m_lock);
pool->m_exitNum = NUMBER;
pthread_mutex_unlock(&pool->m_lock);
for (int i = 0; i < NUMBER; ++i)
{
pthread_cond_signal(&pool->m_notEmpty);
}
}
}
return nullptr;
}
// 线程退出
void ThreadPool::threadExit()
{
pthread_t tid = pthread_self();
for (int i = 0; i < m_maxNum; ++i)
{
if (m_threadIDs[i] == tid)
{
cout << "threadExit() function: thread "
<< to_string(pthread_self()) << " exiting..." << endl;
m_threadIDs[i] = 0;
break;
}
}
pthread_exit(NULL);
}
https://www.cnblogs.com/LaiY9/p/14725352.html
