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/*
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ANDROID_UTILS_SINGLETON_H
#define ANDROID_UTILS_SINGLETON_H
#include <stdint.h>
#include <sys/types.h>
#include <utils/threads.h>
#include <cutils/compiler.h>
namespace android {
// ---------------------------------------------------------------------------
template <typename TYPE>
class ANDROID_API Singleton
{
public:
static TYPE& getInstance() {
Mutex::Autolock _l(sLock);
TYPE* instance = sInstance;
if (instance == 0) {
instance = new TYPE();
sInstance = instance;
}
return *instance;
}
static bool hasInstance() {
Mutex::Autolock _l(sLock);
return sInstance != 0;
}
protected:
~Singleton() { };
Singleton() { };
private:
Singleton(const Singleton&);
Singleton& operator = (const Singleton&);
static Mutex sLock;
static TYPE* sInstance;
};
/*
* use ANDROID_SINGLETON_STATIC_INSTANCE(TYPE) in your implementation file
* (eg: <TYPE>.cpp) to create the static instance of Singleton<>'s attributes,
* and avoid to have a copy of them in each compilation units Singleton<TYPE>
* is used.
* NOTE: we use a version of Mutex ctor that takes a parameter, because
* for some unknown reason using the default ctor doesn't emit the variable!
*/
#define ANDROID_SINGLETON_STATIC_INSTANCE(TYPE) \
template class Singleton< TYPE >; \
template<> Mutex Singleton< TYPE >::sLock(Mutex::PRIVATE); \
template<> TYPE* Singleton< TYPE >::sInstance(0);
// ---------------------------------------------------------------------------
}; // namespace android
#endif // ANDROID_UTILS_SINGLETON_H
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