102 lines
3.1 KiB
C++
102 lines
3.1 KiB
C++
/*
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* Copyright (C) 2007 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ANDROID_UTILS_SINGLETON_H
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#define ANDROID_UTILS_SINGLETON_H
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#include <stdint.h>
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// some vendor code assumes they have atoi() after including this file.
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#include <stdlib.h>
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#include <sys/types.h>
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#include <utils/Mutex.h>
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#include <cutils/compiler.h>
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namespace android {
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// ---------------------------------------------------------------------------
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// Singleton<TYPE> may be used in multiple libraries, only one of which should
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// define the static member variables using ANDROID_SINGLETON_STATIC_INSTANCE.
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// Turn off -Wundefined-var-template so other users don't get:
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// instantiation of variable 'android::Singleton<TYPE>::sLock' required here,
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// but no definition is available
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#if defined(__clang__)
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#pragma clang diagnostic push
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#pragma clang diagnostic ignored "-Wundefined-var-template"
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#endif
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// DO NOT USE: Please use scoped static initialization. For instance:
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// MyClass& getInstance() {
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// static MyClass gInstance(...);
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// return gInstance;
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// }
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template <typename TYPE>
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class ANDROID_API Singleton
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{
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public:
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static TYPE& getInstance() {
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Mutex::Autolock _l(sLock);
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TYPE* instance = sInstance;
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if (instance == nullptr) {
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instance = new TYPE();
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sInstance = instance;
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}
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return *instance;
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}
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static bool hasInstance() {
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Mutex::Autolock _l(sLock);
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return sInstance != nullptr;
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}
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protected:
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~Singleton() { }
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Singleton() { }
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private:
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Singleton(const Singleton&);
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Singleton& operator = (const Singleton&);
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static Mutex sLock;
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static TYPE* sInstance;
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};
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#if defined(__clang__)
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#pragma clang diagnostic pop
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#endif
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/*
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* use ANDROID_SINGLETON_STATIC_INSTANCE(TYPE) in your implementation file
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* (eg: <TYPE>.cpp) to create the static instance of Singleton<>'s attributes,
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* and avoid to have a copy of them in each compilation units Singleton<TYPE>
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* is used.
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* NOTE: we use a version of Mutex ctor that takes a parameter, because
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* for some unknown reason using the default ctor doesn't emit the variable!
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*/
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#define ANDROID_SINGLETON_STATIC_INSTANCE(TYPE) \
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template<> ::android::Mutex \
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(::android::Singleton< TYPE >::sLock)(::android::Mutex::PRIVATE); \
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template<> TYPE* ::android::Singleton< TYPE >::sInstance(nullptr); /* NOLINT */ \
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template class ::android::Singleton< TYPE >;
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// ---------------------------------------------------------------------------
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} // namespace android
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#endif // ANDROID_UTILS_SINGLETON_H
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