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 21 /** 22 * SparseIntArrays map integers to integers. Unlike a normal array of integers, 23 * there can be gaps in the indices. It is intended to be more memory efficient 24 * than using a HashMap to map Integers to Integers, both because it avoids 25 * auto-boxing keys and values and its data structure doesn't rely on an extra entry object 26 * for each mapping. 27 * 28 * <p>Note that this container keeps its mappings in an array data structure, 29 * using a binary search to find keys. The implementation is not intended to be appropriate for 30 * data structures 31 * that may contain large numbers of items. It is generally slower than a traditional 32 * HashMap, since lookups require a binary search and adds and removes require inserting 33 * and deleting entries in the array. For containers holding up to hundreds of items, 34 * the performance difference is not significant, less than 50%.</p> 35 * 36 * <p>It is possible to iterate over the items in this container using 37 * {@link #keyAt(int)} and {@link #valueAt(int)}. Iterating over the keys using 38 * <code>keyAt(int)</code> with ascending values of the index will return the 39 * keys in ascending order, or the values corresponding to the keys in ascending 40 * order in the case of <code>valueAt(int)<code>.</p> 41 */ 42 public class SparseIntArray implements Cloneable { 43 private int[] mKeys; 44 private int[] mValues; 45 private int mSize; 46 47 /** 48 * Creates a new SparseIntArray containing no mappings. 49 */ 50 public SparseIntArray() { 51 this(10); 52 } 53 54 /** 55 * Creates a new SparseIntArray containing no mappings that will not 56 * require any additional memory allocation to store the specified 57 * number of mappings. If you supply an initial capacity of 0, the 58 * sparse array will be initialized with a light-weight representation 59 * not requiring any additional array allocations. 60 */ 61 public SparseIntArray(int initialCapacity) { 62 if (initialCapacity == 0) { 63 mKeys = ContainerHelpers.EMPTY_INTS; 64 mValues = ContainerHelpers.EMPTY_INTS; 65 } else { 66 initialCapacity = ArrayUtils.idealIntArraySize(initialCapacity); 67 mKeys = new int[initialCapacity]; 68 mValues = new int[initialCapacity]; 69 } 70 mSize = 0; 71 } 72 73 @Override 74 public SparseIntArray clone() { 75 SparseIntArray clone = null; 76 try { 77 clone = (SparseIntArray) super.clone(); 78 clone.mKeys = mKeys.clone(); 79 clone.mValues = mValues.clone(); 80 } catch (CloneNotSupportedException cnse) { 81 /* ignore */ 82 } 83 return clone; 84 } 85 86 /** 87 * Gets the int mapped from the specified key, or <code>0</code> 88 * if no such mapping has been made. 89 */ 90 public int get(int key) { 91 return get(key, 0); 92 } 93 94 /** 95 * Gets the int mapped from the specified key, or the specified value 96 * if no such mapping has been made. 97 */ 98 public int get(int key, int valueIfKeyNotFound) { 99 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 100 101 if (i < 0) { 102 return valueIfKeyNotFound; 103 } else { 104 return mValues[i]; 105 } 106 } 107 108 /** 109 * Removes the mapping from the specified key, if there was any. 110 */ 111 public void delete(int key) { 112 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 113 114 if (i >= 0) { 115 removeAt(i); 116 } 117 } 118 119 /** 120 * Removes the mapping at the given index. 121 */ 122 public void removeAt(int index) { 123 System.arraycopy(mKeys, index + 1, mKeys, index, mSize - (index + 1)); 124 System.arraycopy(mValues, index + 1, mValues, index, mSize - (index + 1)); 125 mSize--; 126 } 127 128 /** 129 * Adds a mapping from the specified key to the specified value, 130 * replacing the previous mapping from the specified key if there 131 * was one. 132 */ 133 public void put(int key, int value) { 134 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 135 136 if (i >= 0) { 137 mValues[i] = value; 138 } else { 139 i = ~i; 140 141 if (mSize >= mKeys.length) { 142 int n = ArrayUtils.idealIntArraySize(mSize + 1); 143 144 int[] nkeys = new int[n]; 145 int[] nvalues = new int[n]; 146 147 // Log.e("SparseIntArray", "grow " + mKeys.length + " to " + n); 148 System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length); 149 System.arraycopy(mValues, 0, nvalues, 0, mValues.length); 150 151 mKeys = nkeys; 152 mValues = nvalues; 153 } 154 155 if (mSize - i != 0) { 156 // Log.e("SparseIntArray", "move " + (mSize - i)); 157 System.arraycopy(mKeys, i, mKeys, i + 1, mSize - i); 158 System.arraycopy(mValues, i, mValues, i + 1, mSize - i); 159 } 160 161 mKeys[i] = key; 162 mValues[i] = value; 163 mSize++; 164 } 165 } 166 167 /** 168 * Returns the number of key-value mappings that this SparseIntArray 169 * currently stores. 170 */ 171 public int size() { 172 return mSize; 173 } 174 175 /** 176 * Given an index in the range <code>0...size()-1</code>, returns 177 * the key from the <code>index</code>th key-value mapping that this 178 * SparseIntArray stores. 179 * 180 * <p>The keys corresponding to indices in ascending order are guaranteed to 181 * be in ascending order, e.g., <code>keyAt(0)</code> will return the 182 * smallest key and <code>keyAt(size()-1)</code> will return the largest 183 * key.</p> 184 */ 185 public int keyAt(int index) { 186 return mKeys[index]; 187 } 188 189 /** 190 * Given an index in the range <code>0...size()-1</code>, returns 191 * the value from the <code>index</code>th key-value mapping that this 192 * SparseIntArray stores. 193 * 194 * <p>The values corresponding to indices in ascending order are guaranteed 195 * to be associated with keys in ascending order, e.g., 196 * <code>valueAt(0)</code> will return the value associated with the 197 * smallest key and <code>valueAt(size()-1)</code> will return the value 198 * associated with the largest key.</p> 199 */ 200 public int valueAt(int index) { 201 return mValues[index]; 202 } 203 204 /** 205 * Returns the index for which {@link #keyAt} would return the 206 * specified key, or a negative number if the specified 207 * key is not mapped. 208 */ 209 public int indexOfKey(int key) { 210 return ContainerHelpers.binarySearch(mKeys, mSize, key); 211 } 212 213 /** 214 * Returns an index for which {@link #valueAt} would return the 215 * specified key, or a negative number if no keys map to the 216 * specified value. 217 * Beware that this is a linear search, unlike lookups by key, 218 * and that multiple keys can map to the same value and this will 219 * find only one of them. 220 */ 221 public int indexOfValue(int value) { 222 for (int i = 0; i < mSize; i++) 223 if (mValues[i] == value) 224 return i; 225 226 return -1; 227 } 228 229 /** 230 * Removes all key-value mappings from this SparseIntArray. 231 */ 232 public void clear() { 233 mSize = 0; 234 } 235 236 /** 237 * Puts a key/value pair into the array, optimizing for the case where 238 * the key is greater than all existing keys in the array. 239 */ 240 public void append(int key, int value) { 241 if (mSize != 0 && key <= mKeys[mSize - 1]) { 242 put(key, value); 243 return; 244 } 245 246 int pos = mSize; 247 if (pos >= mKeys.length) { 248 int n = ArrayUtils.idealIntArraySize(pos + 1); 249 250 int[] nkeys = new int[n]; 251 int[] nvalues = new int[n]; 252 253 // Log.e("SparseIntArray", "grow " + mKeys.length + " to " + n); 254 System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length); 255 System.arraycopy(mValues, 0, nvalues, 0, mValues.length); 256 257 mKeys = nkeys; 258 mValues = nvalues; 259 } 260 261 mKeys[pos] = key; 262 mValues[pos] = value; 263 mSize = pos + 1; 264 } 265 266 /** 267 * {@inheritDoc} 268 * 269 * <p>This implementation composes a string by iterating over its mappings. 270 */ 271 @Override 272 public String toString() { 273 if (size() <= 0) { 274 return "{}"; 275 } 276 277 StringBuilder buffer = new StringBuilder(mSize * 28); 278 buffer.append('{'); 279 for (int i=0; i<mSize; i++) { 280 if (i > 0) { 281 buffer.append(", "); 282 } 283 int key = keyAt(i); 284 buffer.append(key); 285 buffer.append('='); 286 int value = valueAt(i); 287 buffer.append(value); 288 } 289 buffer.append('}'); 290 return buffer.toString(); 291 } 292 } 293