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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/Mutex.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;
+};
+
+template <typename TYPE>
+Mutex Singleton<TYPE>::sLock;
+
+template <typename TYPE>
+TYPE* Singleton<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<> ::android::Mutex \
+ (::android::Singleton< TYPE >::sLock)(::android::Mutex::PRIVATE); \
+ template<> TYPE* ::android::Singleton< TYPE >::sInstance(0); \
+ template class ::android::Singleton< TYPE >;
+
+
+// ---------------------------------------------------------------------------
+}; // namespace android
+
+#endif // ANDROID_UTILS_SINGLETON_H
+