Merge "Exporting C++ headers from system/core" am: 812b7d5d52 am: f484dd3401 am: a252f11da3

am: 5a8f555e49

Change-Id: Id449aadc3b9e6e263d351ce031b1f7f7bb4672b8

1 files changed, 85 insertions, 0 deletions

diff --git a/libutils/include/utils/Singleton.h b/libutils/include/utils/Singleton.h
new file mode 100644
index 000000000..7cc4c18be
--- /dev/null
+++ b/libutils/include/utils/Singleton.h
@@ -0,0 +1,85 @@
+/*
+ * 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
+