Singleton.h revision b8510b98b5eb92333157db1359df6f2bbbfb2b39 
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
24namespace android {
25// ---------------------------------------------------------------------------
26
27template <typename TYPE>
28class Singleton
29{
30public:
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
41protected:
42    ~Singleton() { };
43    Singleton() { };
44
45private:
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 * NOTE: we use a version of Mutex ctor that takes a parameter, because
58 * for some unknown reason using the default ctor doesn't emit the variable!
59 */
60
61#define ANDROID_SINGLETON_STATIC_INSTANCE(TYPE)                 \
62    template class Singleton< TYPE >;                           \
63    template<> Mutex Singleton< TYPE >::sLock(Mutex::PRIVATE);  \
64    template<> TYPE* Singleton< TYPE >::sInstance(0);
65
66
67// ---------------------------------------------------------------------------
68}; // namespace android
69
70#endif // ANDROID_UTILS_SINGLETON_H
71
72