ThreadPool.cpp

class Task
{
public:

	Task(int i)
	{
		id = i;
	}

	void virtual run()
	{
		int r = rand() % 3001;
		this_thread::sleep_for(chrono::milliseconds(r));
	}

	int getId()
	{
		return id;
	}
	
private:
	int id;
};

class ThreadPool
{
public:

	ThreadPool& operator=(const ThreadPool&) = delete;
	ThreadPool(const ThreadPool&) = delete;

	ThreadPool()
	{
		for (int i = 0; i < NUM_OF_THREADS; ++i)
		{
			thread th(bind(&ThreadPool::start, this));
			pool.push_back(move(th));
		}
	}

	void execute(Task& task)
	{
		//crucial part
		unique_lock<mutex> lock(m);
		cv.wait(lock, [&] {return q.size() < MAX_CAPACITY; });
		
		cout << "Task " << to_string(task.getId()) << " is added to the blocking queue..." << endl;
		q.push(move(task));
		//notify there is available task
		cv.notify_one();
	}

private:
	queue<Task> q;
	mutex m;
	condition_variable cv;
	const int MAX_CAPACITY = 5;
	const int NUM_OF_THREADS = 6;
	vector<thread> pool;

	void start()
	{
		while (true)
		{
			//crucial part
			unique_lock<mutex> lock(m);
			cv.wait(lock, [&] {return q.size(); });

			Task&& task = move(q.front());
			q.pop();
			//notify there is space to add more tasks
			cout << "Task " << to_string(task.getId()) << " is running..." << endl;
			cv.notify_one();
			lock.unlock();

			//perform task
			task.run();
		}
	}
};

void testThreadPool()
{
	const int NUM_OF_TASKS = 15;
	ThreadPool pool;
	for (int i = 0; i < NUM_OF_TASKS; ++i)
	{
		Task task(i);
		pool.execute(task);
	}
	getchar();
}