/* * Copyright (C) 2007 The Android Open Source Project * * Licensed 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 ANDROID_UTILS_SINGLETON_H #define ANDROID_UTILS_SINGLETON_H #include <stdint.h> #include <sys/types.h> #include <utils/threads.h> namespace android { // --------------------------------------------------------------------------- template <typename TYPE> class Singleton { public: static TYPE& getInstance() { Mutex::Autolock _l(sLock); TYPE* instance = sInstance; if (instance == 0) { instance = new TYPE(); sInstance = instance; } return *instance; } static bool hasInstance() { Mutex::Autolock _l(sLock); return sInstance != 0; } protected: ~Singleton() { }; Singleton() { }; private: Singleton(const Singleton&); Singleton& operator = (const Singleton&); static Mutex sLock; static TYPE* sInstance; }; /* * use ANDROID_SINGLETON_STATIC_INSTANCE(TYPE) in your implementation file * (eg: <TYPE>.cpp) to create the static instance of Singleton<>'s attributes, * and avoid to have a copy of them in each compilation units Singleton<TYPE> * is used. * NOTE: we use a version of Mutex ctor that takes a parameter, because * for some unknown reason using the default ctor doesn't emit the variable! */ #define ANDROID_SINGLETON_STATIC_INSTANCE(TYPE) \ template class Singleton< TYPE >; \ template<> Mutex Singleton< TYPE >::sLock(Mutex::PRIVATE); \ template<> TYPE* Singleton< TYPE >::sInstance(0); // --------------------------------------------------------------------------- }; // namespace android #endif // ANDROID_UTILS_SINGLETON_H