| /* |
| * Copyright (C) 2019 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.display.utils; |
| |
| import java.time.Clock; |
| |
| /** |
| * A fixed-size buffer that keeps the most recent values and their times. |
| * |
| * This class is used for logging and debugging purposes only, so there's no way to retrieve the |
| * history other than toString(), and a non-monotonic clock is good enough. |
| */ |
| public class History { |
| |
| private int mSize; |
| private int mCount; |
| private int mStart; |
| private int mEnd; |
| |
| private long[] mTimes; |
| private float[] mValues; |
| |
| private Clock mClock; |
| |
| /** |
| * @param size |
| * The maximum number of values kept. |
| */ |
| public History(int size) { |
| this(size, Clock.systemUTC()); |
| } |
| |
| /** |
| * @param size |
| * The maximum number of values kept. |
| * @param clock |
| * The clock used. |
| */ |
| public History(int size, Clock clock) { |
| mSize = size; |
| mCount = 0; |
| mStart = 0; |
| mEnd = 0; |
| mTimes = new long[size]; |
| mValues = new float[size]; |
| mClock = clock; |
| } |
| |
| /** |
| * Add a value. |
| * |
| * @param value |
| * The value. |
| */ |
| public void add(float value) { |
| mTimes[mEnd] = mClock.millis(); |
| mValues[mEnd] = value; |
| if (mCount < mSize) { |
| mCount++; |
| } else { |
| mStart = (mStart + 1) % mSize; |
| } |
| mEnd = (mEnd + 1) % mSize; |
| } |
| |
| /** |
| * Convert the buffer to string. |
| * |
| * @return The buffer as string. |
| */ |
| public String toString() { |
| StringBuffer sb = new StringBuffer(); |
| sb.append("["); |
| for (int i = 0; i < mCount; i++) { |
| final int index = (mStart + i) % mSize; |
| final long time = mTimes[index]; |
| final float value = mValues[index]; |
| sb.append(value + " @ " + time); |
| if (i + 1 != mCount) { |
| sb.append(", "); |
| } |
| } |
| sb.append("]"); |
| return sb.toString(); |
| } |
| |
| } |