| /* |
| * Copyright (C) 2016 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.internal.util; |
| |
| /** |
| * Helper class for implementing a ring buffer. This supplies the indices, you supply |
| * the array(s). |
| */ |
| public class RingBufferIndices { |
| private final int mCapacity; |
| |
| // The first valid element and the next open slot. |
| private int mStart; |
| private int mSize; |
| |
| /** |
| * Create ring buffer of the given capacity. |
| */ |
| public RingBufferIndices(int capacity) { |
| mCapacity = capacity; |
| } |
| |
| /** |
| * Add a new item to the ring buffer. If the ring buffer is full, this |
| * replaces the oldest item. |
| * @return Returns the index at which the new item appears, for placing in your array. |
| */ |
| public int add() { |
| if (mSize < mCapacity) { |
| final int pos = mSize; |
| mSize++; |
| return pos; |
| } |
| int pos = mStart; |
| mStart++; |
| if (mStart == mCapacity) { |
| mStart = 0; |
| } |
| return pos; |
| } |
| |
| /** |
| * Clear the ring buffer. |
| */ |
| public void clear() { |
| mStart = 0; |
| mSize = 0; |
| } |
| |
| /** |
| * Return the current size of the ring buffer. |
| */ |
| public int size() { |
| return mSize; |
| } |
| |
| /** |
| * Convert a position in the ring buffer that is [0..size()] to an offset |
| * in the array(s) containing the ring buffer items. |
| */ |
| public int indexOf(int pos) { |
| int index = mStart + pos; |
| if (index >= mCapacity) { |
| index -= mCapacity; |
| } |
| return index; |
| } |
| } |