Initial frameserver/OneCamera integration
Change-Id: I2fe0d8acf9ce927a6a0a1dea599299c715503462
diff --git a/src/com/android/camera/async/Updatable.java b/src/com/android/camera/async/Updatable.java
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+++ b/src/com/android/camera/async/Updatable.java
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+/*
+ * Copyright (C) 2014 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.camera.async;
+
+/**
+ * An interface for updating thread-shared state from producer threads with
+ * real-time requirements.
+ * <p>
+ * Depending on how consumers need to access updates, the following
+ * implementations may be used:
+ * <ul>
+ * <li>Synchronous access to every update: {@link ConcurrentBufferQueue}</li>
+ * <li>Synchronous access to a single update: {@link UpdatableCountDownLatch}</li>
+ * <li>Polling: {@link ConcurrentState}</li>
+ * <li>Callbacks: {@link ConcurrentState}</li>
+ * </ul>
+ * </p>
+ */
+public interface Updatable<T> {
+ /**
+ * Implementations MUST ALWAYS satisfy the following constraints:
+ * <ul>
+ * <li>Return quickly, without performing any expensive work.</li>
+ * <li>Execute in a predictable, stable, amount of time.</li>
+ * <li>Never block.</li>
+ * <li>Be thread-safe.</li>
+ * <li>Never leak control of the thread on which they are invoked. (e.g.
+ * invoke callbacks which may violate the above constraints)</li>
+ * </ul>
+ */
+ public void update(T t);
+}