Initial checkin of AOSP Messaging app.

b/23110861

Change-Id: I11db999bd10656801e618f78ab2b2ef74136fff1

src/com/android/messaging/datamodel/MemoryCacheManager.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2015 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.
+ */
+
+package com.android.messaging.datamodel;
+
+import com.android.messaging.Factory;
+
+import java.util.HashSet;
+
+/**
+ * Utility abstraction which allows MemoryCaches in an application to register and then when there
+ * is memory pressure provide a callback to reclaim the memory in the caches.
+ */
+public class MemoryCacheManager {
+    private final HashSet<MemoryCache> mMemoryCaches = new HashSet<MemoryCache>();
+    private final Object mMemoryCacheLock = new Object();
+
+    public static MemoryCacheManager get() {
+        return Factory.get().getMemoryCacheManager();
+    }
+
+    /**
+     * Extend this interface to provide a reclaim method on a memory cache.
+     */
+    public interface MemoryCache {
+        void reclaim();
+    }
+
+    /**
+     * Register the memory cache with the application.
+     */
+    public void registerMemoryCache(final MemoryCache cache) {
+        synchronized (mMemoryCacheLock) {
+            mMemoryCaches.add(cache);
+        }
+    }
+
+    /**
+     * Unregister the memory cache with the application.
+     */
+    public void unregisterMemoryCache(final MemoryCache cache) {
+        synchronized (mMemoryCacheLock) {
+            mMemoryCaches.remove(cache);
+        }
+    }
+
+    /**
+     * Reclaim memory in all the memory caches in the application.
+     */
+    @SuppressWarnings("unchecked")
+    public void reclaimMemory() {
+        // We're creating a cache copy in the lock to ensure we're not working on a concurrently
+        // modified set, then reclaim outside of the lock to minimize the time within the lock.
+        final HashSet<MemoryCache> shallowCopy;
+        synchronized (mMemoryCacheLock) {
+            shallowCopy = (HashSet<MemoryCache>) mMemoryCaches.clone();
+        }
+        for (final MemoryCache cache : shallowCopy) {
+            cache.reclaim();
+        }
+    }
+}