| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| |
| #ifndef _TUBEMQ_SINGLETON_H |
| #define _TUBEMQ_SINGLETON_H |
| |
| #include <assert.h> |
| #include <stdlib.h> |
| |
| #include <mutex> |
| #include <thread> |
| |
| #include "noncopyable.h" |
| |
| namespace tubemq { |
| |
| template <typename T> |
| class Singleton : noncopyable { |
| public: |
| static T& Instance() { |
| std::call_once(once_, Singleton::init); |
| assert(value_ != nullptr); |
| return *value_; |
| } |
| |
| protected: |
| Singleton() {} |
| ~Singleton() {} |
| |
| private: |
| static void init() { value_ = new T(); } |
| |
| private: |
| static std::once_flag once_; |
| static T* value_; |
| }; |
| |
| template <typename T> |
| std::once_flag Singleton<T>::once_; |
| |
| template <typename T> |
| T* Singleton<T>::value_ = nullptr; |
| |
| } // namespace tubemq |
| |
| #endif // _TUBEMQ_SINGLETON_H |