1 /* 2 * Copyright (C) 2006 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 /** 25 * SparseIntArrays map integers to integers. Unlike a normal array of integers, 26 * there can be gaps in the indices. It is intended to be more memory efficient 27 * than using a HashMap to map Integers to Integers, both because it avoids 28 * auto-boxing keys and values and its data structure doesn't rely on an extra entry object 29 * for each mapping. 30 * 31 * <p>Note that this container keeps its mappings in an array data structure, 32 * using a binary search to find keys. The implementation is not intended to be appropriate for 33 * data structures 34 * that may contain large numbers of items. It is generally slower than a traditional 35 * HashMap, since lookups require a binary search and adds and removes require inserting 36 * and deleting entries in the array. For containers holding up to hundreds of items, 37 * the performance difference is not significant, less than 50%.</p> 38 * 39 * <p>It is possible to iterate over the items in this container using 40 * {@link #keyAt(int)} and {@link #valueAt(int)}. Iterating over the keys using 41 * <code>keyAt(int)</code> with ascending values of the index will return the 42 * keys in ascending order, or the values corresponding to the keys in ascending 43 * order in the case of <code>valueAt(int)</code>.</p> 44 */ 45 public class SparseIntArray implements Cloneable { 46 private int[] mKeys; 47 private int[] mValues; 48 private int mSize; 49 50 /** 51 * Creates a new SparseIntArray containing no mappings. 52 */ SparseIntArray()53 public SparseIntArray() { 54 this(10); 55 } 56 57 /** 58 * Creates a new SparseIntArray containing no mappings that will not 59 * require any additional memory allocation to store the specified 60 * number of mappings. If you supply an initial capacity of 0, the 61 * sparse array will be initialized with a light-weight representation 62 * not requiring any additional array allocations. 63 */ SparseIntArray(int initialCapacity)64 public SparseIntArray(int initialCapacity) { 65 if (initialCapacity == 0) { 66 mKeys = EmptyArray.INT; 67 mValues = EmptyArray.INT; 68 } else { 69 mKeys = ArrayUtils.newUnpaddedIntArray(initialCapacity); 70 mValues = new int[mKeys.length]; 71 } 72 mSize = 0; 73 } 74 75 @Override clone()76 public SparseIntArray clone() { 77 SparseIntArray clone = null; 78 try { 79 clone = (SparseIntArray) super.clone(); 80 clone.mKeys = mKeys.clone(); 81 clone.mValues = mValues.clone(); 82 } catch (CloneNotSupportedException cnse) { 83 /* ignore */ 84 } 85 return clone; 86 } 87 88 /** 89 * Gets the int mapped from the specified key, or <code>0</code> 90 * if no such mapping has been made. 91 */ get(int key)92 public int get(int key) { 93 return get(key, 0); 94 } 95 96 /** 97 * Gets the int mapped from the specified key, or the specified value 98 * if no such mapping has been made. 99 */ get(int key, int valueIfKeyNotFound)100 public int get(int key, int valueIfKeyNotFound) { 101 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 102 103 if (i < 0) { 104 return valueIfKeyNotFound; 105 } else { 106 return mValues[i]; 107 } 108 } 109 110 /** 111 * Removes the mapping from the specified key, if there was any. 112 */ delete(int key)113 public void delete(int key) { 114 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 115 116 if (i >= 0) { 117 removeAt(i); 118 } 119 } 120 121 /** 122 * Removes the mapping at the given index. 123 */ removeAt(int index)124 public void removeAt(int index) { 125 System.arraycopy(mKeys, index + 1, mKeys, index, mSize - (index + 1)); 126 System.arraycopy(mValues, index + 1, mValues, index, mSize - (index + 1)); 127 mSize--; 128 } 129 130 /** 131 * Adds a mapping from the specified key to the specified value, 132 * replacing the previous mapping from the specified key if there 133 * was one. 134 */ put(int key, int value)135 public void put(int key, int value) { 136 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 137 138 if (i >= 0) { 139 mValues[i] = value; 140 } else { 141 i = ~i; 142 143 mKeys = GrowingArrayUtils.insert(mKeys, mSize, i, key); 144 mValues = GrowingArrayUtils.insert(mValues, mSize, i, value); 145 mSize++; 146 } 147 } 148 149 /** 150 * Returns the number of key-value mappings that this SparseIntArray 151 * currently stores. 152 */ size()153 public int size() { 154 return mSize; 155 } 156 157 /** 158 * Given an index in the range <code>0...size()-1</code>, returns 159 * the key from the <code>index</code>th key-value mapping that this 160 * SparseIntArray stores. 161 * 162 * <p>The keys corresponding to indices in ascending order are guaranteed to 163 * be in ascending order, e.g., <code>keyAt(0)</code> will return the 164 * smallest key and <code>keyAt(size()-1)</code> will return the largest 165 * key.</p> 166 */ keyAt(int index)167 public int keyAt(int index) { 168 return mKeys[index]; 169 } 170 171 /** 172 * Given an index in the range <code>0...size()-1</code>, returns 173 * the value from the <code>index</code>th key-value mapping that this 174 * SparseIntArray stores. 175 * 176 * <p>The values corresponding to indices in ascending order are guaranteed 177 * to be associated with keys in ascending order, e.g., 178 * <code>valueAt(0)</code> will return the value associated with the 179 * smallest key and <code>valueAt(size()-1)</code> will return the value 180 * associated with the largest key.</p> 181 */ valueAt(int index)182 public int valueAt(int index) { 183 return mValues[index]; 184 } 185 186 /** 187 * Directly set the value at a particular index. 188 * @hide 189 */ setValueAt(int index, int value)190 public void setValueAt(int index, int value) { 191 mValues[index] = value; 192 } 193 194 /** 195 * Returns the index for which {@link #keyAt} would return the 196 * specified key, or a negative number if the specified 197 * key is not mapped. 198 */ indexOfKey(int key)199 public int indexOfKey(int key) { 200 return ContainerHelpers.binarySearch(mKeys, mSize, key); 201 } 202 203 /** 204 * Returns an index for which {@link #valueAt} would return the 205 * specified key, or a negative number if no keys map to the 206 * specified value. 207 * Beware that this is a linear search, unlike lookups by key, 208 * and that multiple keys can map to the same value and this will 209 * find only one of them. 210 */ indexOfValue(int value)211 public int indexOfValue(int value) { 212 for (int i = 0; i < mSize; i++) 213 if (mValues[i] == value) 214 return i; 215 216 return -1; 217 } 218 219 /** 220 * Removes all key-value mappings from this SparseIntArray. 221 */ clear()222 public void clear() { 223 mSize = 0; 224 } 225 226 /** 227 * Puts a key/value pair into the array, optimizing for the case where 228 * the key is greater than all existing keys in the array. 229 */ append(int key, int value)230 public void append(int key, int value) { 231 if (mSize != 0 && key <= mKeys[mSize - 1]) { 232 put(key, value); 233 return; 234 } 235 236 mKeys = GrowingArrayUtils.append(mKeys, mSize, key); 237 mValues = GrowingArrayUtils.append(mValues, mSize, value); 238 mSize++; 239 } 240 241 /** 242 * {@inheritDoc} 243 * 244 * <p>This implementation composes a string by iterating over its mappings. 245 */ 246 @Override toString()247 public String toString() { 248 if (size() <= 0) { 249 return "{}"; 250 } 251 252 StringBuilder buffer = new StringBuilder(mSize * 28); 253 buffer.append('{'); 254 for (int i=0; i<mSize; i++) { 255 if (i > 0) { 256 buffer.append(", "); 257 } 258 int key = keyAt(i); 259 buffer.append(key); 260 buffer.append('='); 261 int value = valueAt(i); 262 buffer.append(value); 263 } 264 buffer.append('}'); 265 return buffer.toString(); 266 } 267 } 268