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      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 
     24 namespace android {
     25 // ---------------------------------------------------------------------------
     26 
     27 template <typename TYPE>
     28 class Singleton
     29 {
     30 public:
     31     static TYPE& getInstance() {
     32         Mutex::Autolock _l(sLock);
     33         TYPE* instance = sInstance;
     34         if (instance == 0) {
     35             instance = new TYPE();
     36             sInstance = instance;
     37         }
     38         return *instance;
     39     }
     40 
     41 protected:
     42     ~Singleton() { };
     43     Singleton() { };
     44 
     45 private:
     46     Singleton(const Singleton&);
     47     Singleton& operator = (const Singleton&);
     48     static Mutex sLock;
     49     static TYPE* sInstance;
     50 };
     51 
     52 /*
     53  * use ANDROID_SINGLETON_STATIC_INSTANCE(TYPE) in your implementation file
     54  * (eg: <TYPE>.cpp) to create the static instance of Singleton<>'s attributes,
     55  * and avoid to have a copy of them in each compilation units Singleton<TYPE>
     56  * is used.
     57  */
     58 
     59 #define ANDROID_SINGLETON_STATIC_INSTANCE(TYPE)             \
     60     template class Singleton< TYPE >;                       \
     61     template< class TYPE > Mutex Singleton< TYPE >::sLock;  \
     62     template<> TYPE* Singleton< TYPE >::sInstance(0);
     63 
     64 
     65 // ---------------------------------------------------------------------------
     66 }; // namespace android
     67 
     68 #endif // ANDROID_UTILS_SINGLETON_H
     69 
     70