Puneet Lall | 9c94ab3 | 2014-12-02 13:12:53 -0800 | [diff] [blame] | 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 | |
| 17 | package 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 | */ |
| 33 | public 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 | } |