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
25namespace android {
26// ---------------------------------------------------------------------------
27
28template <typename TYPE>
29class ANDROID_API Singleton
30{
31public:
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
42    static bool hasInstance() {
43        Mutex::Autolock _l(sLock);
44        return sInstance != 0;
45    }
46
47protected:
48    ~Singleton() { };
49    Singleton() { };
50
51private:
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<> Mutex Singleton< TYPE >::sLock(Mutex::PRIVATE);  \
69    template<> TYPE* Singleton< TYPE >::sInstance(0);           \
70    template class Singleton< TYPE >;
71
72
73// ---------------------------------------------------------------------------
74}; // namespace android
75
76#endif // ANDROID_UTILS_SINGLETON_H
77
78