| /* |
| * Copyright (C) 2018 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.server.wm.utils; |
| |
| import android.util.SparseArray; |
| |
| import java.util.Arrays; |
| |
| /** |
| * Caches the result of a rotation-dependent computation. |
| * |
| * The cache is discarded once the identity of the other parameter changes. |
| * |
| * @param <T> type of the parameter to the computation |
| * @param <R> type of the result of the computation |
| */ |
| public class RotationCache<T,R> { |
| |
| private final RotationDependentComputation<T,R> mComputation; |
| private final SparseArray<R> mCache = new SparseArray<>(4); |
| private T mCachedFor; |
| |
| public RotationCache(RotationDependentComputation<T, R> computation) { |
| mComputation = computation; |
| } |
| |
| /** |
| * Looks up the result of the computation, or calculates it if needed. |
| * |
| * @param t a parameter to the rotation-dependent computation. |
| * @param rotation the rotation for which to perform the rotation-dependent computation. |
| * @return the result of the rotation-dependent computation. |
| */ |
| public R getOrCompute(T t, int rotation) { |
| if (t != mCachedFor) { |
| mCache.clear(); |
| mCachedFor = t; |
| } |
| final int idx = mCache.indexOfKey(rotation); |
| if (idx >= 0) { |
| return mCache.valueAt(idx); |
| } |
| final R result = mComputation.compute(t, rotation); |
| mCache.put(rotation, result); |
| return result; |
| } |
| |
| /** |
| * A computation that takes a generic input and is dependent on the rotation. The result can |
| * be cached by {@link RotationCache}. |
| */ |
| @FunctionalInterface |
| public interface RotationDependentComputation<T, R> { |
| R compute(T t, int rotation); |
| } |
| } |