Updatable.java revision 9c94ab32a69a1ad3642a0f1e38e68bcfd97d3511
1/* 2 * Copyright (C) 2014 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package com.android.camera.async; 18 19/** 20 * An interface for updating thread-shared state from producer threads with 21 * real-time requirements. 22 * <p> 23 * Depending on how consumers need to access updates, the following 24 * implementations may be used: 25 * <ul> 26 * <li>Synchronous access to every update: {@link ConcurrentBufferQueue}</li> 27 * <li>Synchronous access to a single update: {@link UpdatableCountDownLatch}</li> 28 * <li>Polling: {@link ConcurrentState}</li> 29 * <li>Callbacks: {@link ConcurrentState}</li> 30 * </ul> 31 * </p> 32 */ 33public interface Updatable<T> { 34 /** 35 * Implementations MUST ALWAYS satisfy the following constraints: 36 * <ul> 37 * <li>Return quickly, without performing any expensive work.</li> 38 * <li>Execute in a predictable, stable, amount of time.</li> 39 * <li>Never block.</li> 40 * <li>Be thread-safe.</li> 41 * <li>Never leak control of the thread on which they are invoked. (e.g. 42 * invoke callbacks which may violate the above constraints)</li> 43 * </ul> 44 */ 45 public void update(T t); 46} 47