axmol/cocos/base/CCAsyncTaskPool.h

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Copyright (c) 2010      cocos2d-x.org
Copyright (c) 2013-2014 Chukong Technologies Inc.

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#ifndef __CCSYNC_TASK_POOL_H_
#define __CCSYNC_TASK_POOL_H_

#include "platform/CCPlatformMacros.h"
#include "base/CCRef.h"
#include <vector>
#include <queue>
#include <memory>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <future>
#include <functional>
#include <stdexcept>

NS_CC_BEGIN
/////////////////////////////////////////////////////////////////////////////

class AsyncTaskPool
{
public:
    typedef std::function<void(void*)> TaskCallBack;
    
    enum class TaskType
    {
        TASK_IO,
        TASK_NETWORK,
        TASK_OTHER,
        TASK_MAX_TYPE,
    };
    /**
     * get instance
     */
    static AsyncTaskPool* getInstance();
    /**
     * destroy instance
     */
    static void destoryInstance();
    
    /**
     * get max number of call back per process, -1 means unlimited (-1 is the default value)
     */
    static int getMaxTaskCallBackPerProcess();
    
    /**
     * set max number of call back per process, -1 means unlimited
     */
    static void setMaxTaskCallBackPerProcess(int numTaskCallBack);
    
    /**
     * process the call back after task, this should be called in the main thread
     */
    void processTaskCallBack()
    {
        _taskcallbackDispatcher.update();
    }
    
    /**
     * enqueue a asynchronous task
     * @param type task type is io task, network task or others, each type of task has a thread to deal with it.
     * @param callback callback when the task is finished. The callback is called in the main thread instead of task thread
     * @param callbackParam parameter used by the callback
     * @param f task can be lambda function
     * @param args task parameters
     */
    template<class F, class... Args>
    inline void enqueue(TaskType type, const TaskCallBack& callback, void* callbackParam, F&& f, Args&&... args);
    
CC_CONSTRUCTOR_ACCESS:
    AsyncTaskPool();
    ~AsyncTaskPool();
    
protected:
    struct AsyncTaskCallBack
    {
        TaskCallBack          callback;
        void*                 callbackParam;
    };
    
    // thread tasks internally used
    class ThreadTasks {
        friend class AsyncTaskPool;
    public:
        ThreadTasks()
        : _stop(false)
        {
            _thread = std::thread(
                                  [this]
                                  {
                                      for(;;)
                                      {
                                          std::function<void()> task;
                                          AsyncTaskCallBack callback;
                                          {
                                              std::unique_lock<std::mutex> lock(this->_queue_mutex);
                                              this->_condition.wait(lock,
                                                                    [this]{ return this->_stop || !this->_tasks.empty(); });
                                              if(this->_stop && this->_tasks.empty())
                                                  return;
                                              task = std::move(this->_tasks.front());
                                              callback = std::move(this->_taskCallBacks.front());
                                              this->_tasks.pop();
                                              this->_taskCallBacks.pop();
                                          }
                                          
                                          task();
                                          AsyncTaskPool::getInstance()->_taskcallbackDispatcher.enqueue(callback);
                                          //task();
                                      }
                                  }
                                  );
        }
        ~ThreadTasks()
        {
            {
                std::unique_lock<std::mutex> lock(_queue_mutex);
                _stop = true;
                while(_tasks.size())_tasks.pop();
                while (_taskCallBacks.size()) {
                    _taskCallBacks.pop();
                }
            }
            _condition.notify_all();
            _thread.join();
        }
    private:
        
        // need to keep track of thread so we can join them
        std::thread _thread;
        // the task queue
        std::queue< std::function<void()> > _tasks;
        std::queue<AsyncTaskCallBack>            _taskCallBacks;
//        std::queue< AsyncTask > _tasks;
        
        // synchronization
        std::mutex _queue_mutex;
        std::condition_variable _condition;
        bool _stop;
    };
    
    class AfterAsyncTaskDispatcher
    {
    public:
        void update()
        {
            if (_callBacks.empty())
                return;
            
            std::unique_lock<std::mutex> lock(_queue_mutex);
            int numCallBack = 0;
            
            for (auto& it : _callBacks) {
                numCallBack++;
                if (s_maxCallBackPerProcess != -1 && numCallBack > s_maxCallBackPerProcess)
                    break;
                
                if (it.callback)
                {
                    it.callback(it.callbackParam);
                }
            }
            
            _callBacks.erase(_callBacks.begin(), _callBacks.begin() + numCallBack);
        }
        
        AfterAsyncTaskDispatcher() {}
        ~AfterAsyncTaskDispatcher() {}
        
        void enqueue(const AsyncTaskCallBack& callback)
        {
            std::unique_lock<std::mutex> lock(_queue_mutex);
            _callBacks.push_back(callback);
        }
        
    protected:
        
        std::vector<AsyncTaskCallBack> _callBacks;
        std::mutex _queue_mutex;
    };
    
    //tasks
    //ThreadTasks _threadTasks[int(TaskType::TASK_MAX_TYPE)];
    ThreadTasks *_threadTasks;
    //deal task call back
    AfterAsyncTaskDispatcher _taskcallbackDispatcher;
    static AsyncTaskPool* s_asyncTaskPool;
    static int s_maxCallBackPerProcess;
};

template<class F, class... Args>
inline void AsyncTaskPool::enqueue(AsyncTaskPool::TaskType type, const TaskCallBack& callback, void* callbackParam, F&& f, Args&&... args)
{
    auto& threadTask = _threadTasks[(int)type];
    //return _threadTasks[taskType].enqueue(f, args);
    
    using return_type = typename std::result_of<F(Args...)>::type;
    
    auto task = std::bind(std::forward<F>(f), std::forward<Args>(args)...);
    
    auto& queue_mutex = threadTask._queue_mutex;
    auto& stop = threadTask._stop;
    auto& tasks = threadTask._tasks;
    auto& condition = threadTask._condition;
    auto& taskcallbacks = threadTask._taskCallBacks;
    
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        
        // don't allow enqueueing after stopping the pool
        if(stop)
        {
            CC_ASSERT(0 && "already stop");
            return;
        }
        
        AsyncTaskCallBack taskCallBack;
        taskCallBack.callback = callback;
        taskCallBack.callbackParam = callbackParam;
        tasks.emplace([task](){ task(); });
        taskcallbacks.emplace(taskCallBack);
    }
    condition.notify_one();
}

NS_CC_END
#endif //__CCSYNC_TASK_POOL_H_