2 * Copyright (C) 2007 The Android Open Source Project
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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
17 #ifndef ANDROID_UTILS_SINGLETON_H
18 #define ANDROID_UTILS_SINGLETON_H
21 #include <sys/types.h>
22 #include <utils/threads.h>
23 #include <cutils/compiler.h>
26 // ---------------------------------------------------------------------------
28 template <typename TYPE>
29 class ANDROID_API Singleton
32 static TYPE& getInstance() {
33 Mutex::Autolock _l(sLock);
34 TYPE* instance = sInstance;
36 instance = new TYPE();
42 static bool hasInstance() {
43 Mutex::Autolock _l(sLock);
44 return sInstance != 0;
52 Singleton(const Singleton&);
53 Singleton& operator = (const Singleton&);
55 static TYPE* sInstance;
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>
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!
67 #define ANDROID_SINGLETON_STATIC_INSTANCE(TYPE) \
68 template<> Mutex Singleton< TYPE >::sLock(Mutex::PRIVATE); \
69 template<> TYPE* Singleton< TYPE >::sInstance(0); \
70 template class Singleton< TYPE >;
73 // ---------------------------------------------------------------------------
74 }; // namespace android
76 #endif // ANDROID_UTILS_SINGLETON_H