Suprabh Shukla | 47ca6fc | 2019-01-15 18:15:10 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2019 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 android.util; |
| 18 | |
| 19 | import com.android.internal.util.ArrayUtils; |
| 20 | import com.android.internal.util.GrowingArrayUtils; |
| 21 | |
| 22 | import libcore.util.EmptyArray; |
| 23 | |
| 24 | import java.util.NoSuchElementException; |
| 25 | |
| 26 | /** |
| 27 | * A lightweight implementation for a queue with long values. |
| 28 | * Additionally supports getting an element with a specified position from the head of the queue. |
| 29 | * The queue grows in size if needed to accommodate new elements. |
| 30 | * |
| 31 | * @hide |
| 32 | */ |
| 33 | public class LongArrayQueue { |
| 34 | |
| 35 | private long[] mValues; |
| 36 | private int mSize; |
| 37 | private int mHead; |
| 38 | private int mTail; |
| 39 | |
| 40 | /** |
| 41 | * Initializes a queue with the given starting capacity. |
| 42 | * |
| 43 | * @param initialCapacity the capacity. |
| 44 | */ |
| 45 | public LongArrayQueue(int initialCapacity) { |
| 46 | if (initialCapacity == 0) { |
| 47 | mValues = EmptyArray.LONG; |
| 48 | } else { |
| 49 | mValues = ArrayUtils.newUnpaddedLongArray(initialCapacity); |
| 50 | } |
| 51 | mSize = 0; |
| 52 | mHead = mTail = 0; |
| 53 | } |
| 54 | |
| 55 | /** |
| 56 | * Initializes a queue with default starting capacity. |
| 57 | */ |
| 58 | public LongArrayQueue() { |
| 59 | this(16); |
| 60 | } |
| 61 | |
| 62 | private void grow() { |
| 63 | if (mSize < mValues.length) { |
| 64 | throw new IllegalStateException("Queue not full yet!"); |
| 65 | } |
| 66 | final int newSize = GrowingArrayUtils.growSize(mSize); |
| 67 | final long[] newArray = ArrayUtils.newUnpaddedLongArray(newSize); |
| 68 | final int r = mValues.length - mHead; // Number of elements on and to the right of head. |
| 69 | System.arraycopy(mValues, mHead, newArray, 0, r); |
| 70 | System.arraycopy(mValues, 0, newArray, r, mHead); |
| 71 | mValues = newArray; |
| 72 | mHead = 0; |
| 73 | mTail = mSize; |
| 74 | } |
| 75 | |
| 76 | /** |
| 77 | * Returns the number of elements in the queue. |
| 78 | */ |
| 79 | public int size() { |
| 80 | return mSize; |
| 81 | } |
| 82 | |
| 83 | /** |
| 84 | * Removes all elements from this queue. |
| 85 | */ |
| 86 | public void clear() { |
| 87 | mSize = 0; |
| 88 | mHead = mTail = 0; |
| 89 | } |
| 90 | |
| 91 | /** |
| 92 | * Adds a value to the tail of the queue. |
| 93 | * |
| 94 | * @param value the value to be added. |
| 95 | */ |
| 96 | public void addLast(long value) { |
| 97 | if (mSize == mValues.length) { |
| 98 | grow(); |
| 99 | } |
| 100 | mValues[mTail] = value; |
| 101 | mTail = (mTail + 1) % mValues.length; |
| 102 | mSize++; |
| 103 | } |
| 104 | |
| 105 | /** |
| 106 | * Removes an element from the head of the queue. |
| 107 | * |
| 108 | * @return the element at the head of the queue. |
| 109 | * @throws NoSuchElementException if the queue is empty. |
| 110 | */ |
| 111 | public long removeFirst() { |
| 112 | if (mSize == 0) { |
| 113 | throw new NoSuchElementException("Queue is empty!"); |
| 114 | } |
| 115 | final long ret = mValues[mHead]; |
| 116 | mHead = (mHead + 1) % mValues.length; |
| 117 | mSize--; |
| 118 | return ret; |
| 119 | } |
| 120 | |
| 121 | /** |
| 122 | * Returns the element at the given position from the head of the queue, where 0 represents the |
| 123 | * head of the queue. |
| 124 | * |
| 125 | * @param position the position from the head of the queue. |
| 126 | * @return the element found at the given position. |
| 127 | * @throws IndexOutOfBoundsException if {@code position} < {@code 0} or |
| 128 | * {@code position} >= {@link #size()} |
| 129 | */ |
| 130 | public long get(int position) { |
| 131 | if (position < 0 || position >= mSize) { |
| 132 | throw new IndexOutOfBoundsException("Index " + position |
| 133 | + " not valid for a queue of size " + mSize); |
| 134 | } |
| 135 | final int index = (mHead + position) % mValues.length; |
| 136 | return mValues[index]; |
| 137 | } |
| 138 | |
| 139 | /** |
| 140 | * Returns the element at the head of the queue, without removing it. |
| 141 | * |
| 142 | * @return the element at the head of the queue. |
| 143 | * @throws NoSuchElementException if the queue is empty |
| 144 | */ |
| 145 | public long peekFirst() { |
| 146 | if (mSize == 0) { |
| 147 | throw new NoSuchElementException("Queue is empty!"); |
| 148 | } |
| 149 | return mValues[mHead]; |
| 150 | } |
| 151 | |
| 152 | /** |
| 153 | * Returns the element at the tail of the queue. |
| 154 | * |
| 155 | * @return the element at the tail of the queue. |
| 156 | * @throws NoSuchElementException if the queue is empty. |
| 157 | */ |
| 158 | public long peekLast() { |
| 159 | if (mSize == 0) { |
| 160 | throw new NoSuchElementException("Queue is empty!"); |
| 161 | } |
| 162 | final int index = (mTail == 0) ? mValues.length - 1 : mTail - 1; |
| 163 | return mValues[index]; |
| 164 | } |
Kweku Adams | 5ea4228 | 2019-12-13 18:06:03 -0800 | [diff] [blame] | 165 | |
| 166 | /** |
| 167 | * {@inheritDoc} |
| 168 | */ |
| 169 | @Override |
| 170 | public String toString() { |
| 171 | if (mSize <= 0) { |
| 172 | return "{}"; |
| 173 | } |
| 174 | |
| 175 | final StringBuilder buffer = new StringBuilder(mSize * 64); |
| 176 | buffer.append('{'); |
| 177 | buffer.append(get(0)); |
| 178 | for (int i = 1; i < mSize; i++) { |
| 179 | buffer.append(", "); |
| 180 | buffer.append(get(i)); |
| 181 | } |
| 182 | buffer.append('}'); |
| 183 | return buffer.toString(); |
| 184 | } |
Suprabh Shukla | 47ca6fc | 2019-01-15 18:15:10 -0800 | [diff] [blame] | 185 | } |