1 /* 2 * Copyright (C) 2007 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ANDROID_UTILS_SINGLETON_H 18 #define ANDROID_UTILS_SINGLETON_H 19 20 #include <stdint.h> 21 #include <sys/types.h> 22 #include <utils/threads.h> 23 #include <cutils/compiler.h> 24 25 namespace android { 26 // --------------------------------------------------------------------------- 27 28 template <typename TYPE> 29 class ANDROID_API Singleton 30 { 31 public: getInstance()32 static TYPE& getInstance() { 33 Mutex::Autolock _l(sLock); 34 TYPE* instance = sInstance; 35 if (instance == 0) { 36 instance = new TYPE(); 37 sInstance = instance; 38 } 39 return *instance; 40 } 41 hasInstance()42 static bool hasInstance() { 43 Mutex::Autolock _l(sLock); 44 return sInstance != 0; 45 } 46 47 protected: ~Singleton()48 ~Singleton() { }; Singleton()49 Singleton() { }; 50 51 private: 52 Singleton(const Singleton&); 53 Singleton& operator = (const Singleton&); 54 static Mutex sLock; 55 static TYPE* sInstance; 56 }; 57 58 /* 59 * use ANDROID_SINGLETON_STATIC_INSTANCE(TYPE) in your implementation file 60 * (eg: <TYPE>.cpp) to create the static instance of Singleton<>'s attributes, 61 * and avoid to have a copy of them in each compilation units Singleton<TYPE> 62 * is used. 63 * NOTE: we use a version of Mutex ctor that takes a parameter, because 64 * for some unknown reason using the default ctor doesn't emit the variable! 65 */ 66 67 #define ANDROID_SINGLETON_STATIC_INSTANCE(TYPE) \ 68 template class Singleton< TYPE >; \ 69 template<> Mutex Singleton< TYPE >::sLock(Mutex::PRIVATE); \ 70 template<> TYPE* Singleton< TYPE >::sInstance(0); 71 72 73 // --------------------------------------------------------------------------- 74 }; // namespace android 75 76 #endif // ANDROID_UTILS_SINGLETON_H 77 78