83 lines
2.1 KiB
Java
83 lines
2.1 KiB
Java
/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License
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*/
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package com.android.internal.util;
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/**
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* Helper class for implementing a ring buffer. This supplies the indices, you supply
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* the array(s).
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*/
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public class RingBufferIndices {
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private final int mCapacity;
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// The first valid element and the next open slot.
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private int mStart;
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private int mSize;
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/**
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* Create ring buffer of the given capacity.
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*/
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public RingBufferIndices(int capacity) {
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mCapacity = capacity;
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}
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/**
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* Add a new item to the ring buffer. If the ring buffer is full, this
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* replaces the oldest item.
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* @return Returns the index at which the new item appears, for placing in your array.
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*/
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public int add() {
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if (mSize < mCapacity) {
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final int pos = mSize;
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mSize++;
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return pos;
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}
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int pos = mStart;
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mStart++;
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if (mStart == mCapacity) {
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mStart = 0;
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}
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return pos;
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}
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/**
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* Clear the ring buffer.
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*/
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public void clear() {
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mStart = 0;
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mSize = 0;
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}
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/**
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* Return the current size of the ring buffer.
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*/
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public int size() {
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return mSize;
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}
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/**
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* Convert a position in the ring buffer that is [0..size()] to an offset
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* in the array(s) containing the ring buffer items.
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*/
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public int indexOf(int pos) {
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int index = mStart + pos;
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if (index >= mCapacity) {
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index -= mCapacity;
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}
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return index;
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}
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}
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