ZLMediaKit 全局事件通知机制

川长思鸟来 2022-09-04 04:58 222阅读 0赞

最近看ZLMediaKit事件通知机制，发现挺好，跟Java的EventBus优点类似。  
这个主要用回调函数注册事件，当事件发生的时候，通过emitEvent（）函数执行回调函数。  
NoticeCenter类是个单例全局类，其提供了addListener（），delListener（），通过者两个函数控制监听者  
这是一个全局事件通知框架，无任何第三方依赖，先贴出代码：

/* * Copyright (c) 2016 The ZLToolKit project authors. All Rights Reserved. * * This file is part of ZLToolKit(https://github.com/xia-chu/ZLToolKit). * * Use of this source code is governed by MIT license that can be found in the * LICENSE file in the root of the source tree. All contributing project authors * may be found in the AUTHORS file in the root of the source tree. */
    
    #ifndef SRC_UTIL_NOTICECENTER_H_
    #define SRC_UTIL_NOTICECENTER_H_
    
    #include <mutex>
    #include <memory>
    #include <string>
    #include <exception>
    #include <functional>
    #include <unordered_map>
    #include <thread>
    #include "function_traits.h"
    #include "onceToken.h"
    using namespace std;
    
    namespace toolkit { 
    
    class EventDispatcher { 
    public:
        friend class NoticeCenter;
        typedef std::shared_ptr<EventDispatcher> Ptr;
        ~EventDispatcher() = default;
    
    private:
        typedef unordered_multimap<void *, std::shared_ptr<void> > MapType;
        EventDispatcher() = default;
    
        class InterruptException : public std::runtime_error { 
        public:
            InterruptException() : std::runtime_error("InterruptException") { }
            ~InterruptException() { }
        };
    
        template<typename ...ArgsType>
        int emitEvent(ArgsType &&...args) { 
            typedef function<void(decltype(std::forward<ArgsType>(args))...)> funType;
            decltype(_mapListener) copy;
            { 
                //先拷贝(开销比较小)，目的是防止在触发回调时还是上锁状态从而导致交叉互锁
                lock_guard<recursive_mutex> lck(_mtxListener);
                copy = _mapListener;
            }
    
            int ret = 0;
            for (auto &pr : copy) { 
                funType *obj = (funType *) (pr.second.get());
                try { 
                    (*obj)(std::forward<ArgsType>(args)...);
                    ++ret;
                } catch (InterruptException &) { 
                    ++ret;
                    break;
                }
            }
            return ret;
        }
    
        template<typename FUNC>
        void addListener(void *tag, FUNC &&func) { 
            typedef typename function_traits<typename std::remove_reference<FUNC>::type>::stl_function_type funType;
            std::shared_ptr<void> pListener(new funType(std::forward<FUNC>(func)), [](void *ptr) { 
                funType *obj = (funType *) ptr;
                delete obj;
            });
            lock_guard<recursive_mutex> lck(_mtxListener);
            _mapListener.emplace(tag, pListener);
        }
    
        void delListener(void *tag, bool &empty) { 
            lock_guard<recursive_mutex> lck(_mtxListener);
            _mapListener.erase(tag);
            empty = _mapListener.empty();
        }
    
    private:
        recursive_mutex _mtxListener;
        MapType _mapListener;
    };
    
    class NoticeCenter : public std::enable_shared_from_this<NoticeCenter> { 
    public:
        typedef std::shared_ptr<NoticeCenter> Ptr;
        ~NoticeCenter() { }
        static NoticeCenter &Instance();
    
        template<typename ...ArgsType>
        int emitEvent(const string &strEvent, ArgsType &&...args) { 
            auto dispatcher = getDispatcher(strEvent);
            if (!dispatcher) { 
                //该事件无人监听
                return 0;
            }
            return dispatcher->emitEvent(std::forward<ArgsType>(args)...);
        }
    
        template<typename FUNC>
        void addListener(void *tag, const string &event, FUNC &&func) { 
            getDispatcher(event, true)->addListener(tag, std::forward<FUNC>(func));
        }
    
        void delListener(void *tag, const string &event) { 
            auto dispatcher = getDispatcher(event);
            if (!dispatcher) { 
                //不存在该事件
                return;
            }
            bool empty;
            dispatcher->delListener(tag, empty);
            if (empty) { 
                delDispatcher(event, dispatcher);
            }
        }
    
        //这个方法性能比较差
        void delListener(void *tag) { 
            lock_guard<recursive_mutex> lck(_mtxListener);
            bool empty;
            for (auto it = _mapListener.begin(); it != _mapListener.end();) { 
                it->second->delListener(tag, empty);
                if (empty) { 
                    it = _mapListener.erase(it);
                    continue;
                }
                ++it;
            }
        }
    
        void clearAll() { 
            lock_guard<recursive_mutex> lck(_mtxListener);
            _mapListener.clear();
        }
    private:
        EventDispatcher::Ptr getDispatcher(const string &event, bool create = false) { 
            lock_guard<recursive_mutex> lck(_mtxListener);
            auto it = _mapListener.find(event);
            if (it != _mapListener.end()) { 
                return it->second;
            }
            if (create) { 
                //如果为空则创建一个
                EventDispatcher::Ptr dispatcher(new EventDispatcher());
                _mapListener.emplace(event, dispatcher);
                return dispatcher;
            }
            return nullptr;
        }
    
        void delDispatcher(const string &event, const EventDispatcher::Ptr &dispatcher) { 
            lock_guard<recursive_mutex> lck(_mtxListener);
            auto it = _mapListener.find(event);
            if (it != _mapListener.end() && dispatcher == it->second) { 
                //两者相同则删除
                _mapListener.erase(it);
            }
        }
    
        NoticeCenter() { }
    private:
        recursive_mutex _mtxListener;
        unordered_map<string, EventDispatcher::Ptr> _mapListener;
    };
    
    } /* namespace toolkit */
    #endif /* SRC_UTIL_NOTICECENTER_H_ */