SparseArray.java revision c801768e4d29667a2608695449ebc2833ba0f200
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 17package android.util; 18 19import com.android.internal.util.ArrayUtils; 20 21/** 22 * SparseArrays map integers to Objects. Unlike a normal array of Objects, 23 * there can be gaps in the indices. It is intended to be more efficient 24 * than using a HashMap to map Integers to Objects. 25 */ 26public class SparseArray<E> { 27 private static final Object DELETED = new Object(); 28 private boolean mGarbage = false; 29 30 /** 31 * Creates a new SparseArray containing no mappings. 32 */ 33 public SparseArray() { 34 this(10); 35 } 36 37 /** 38 * Creates a new SparseArray containing no mappings that will not 39 * require any additional memory allocation to store the specified 40 * number of mappings. 41 */ 42 public SparseArray(int initialCapacity) { 43 initialCapacity = ArrayUtils.idealIntArraySize(initialCapacity); 44 45 mKeys = new int[initialCapacity]; 46 mValues = new Object[initialCapacity]; 47 mSize = 0; 48 } 49 50 /** 51 * Gets the Object mapped from the specified key, or <code>null</code> 52 * if no such mapping has been made. 53 */ 54 public E get(int key) { 55 return get(key, null); 56 } 57 58 /** 59 * Gets the Object mapped from the specified key, or the specified Object 60 * if no such mapping has been made. 61 */ 62 public E get(int key, E valueIfKeyNotFound) { 63 int i = binarySearch(mKeys, 0, mSize, key); 64 65 if (i < 0 || mValues[i] == DELETED) { 66 return valueIfKeyNotFound; 67 } else { 68 return (E) mValues[i]; 69 } 70 } 71 72 /** 73 * Removes the mapping from the specified key, if there was any. 74 */ 75 public void delete(int key) { 76 int i = binarySearch(mKeys, 0, mSize, key); 77 78 if (i >= 0) { 79 if (mValues[i] != DELETED) { 80 mValues[i] = DELETED; 81 mGarbage = true; 82 } 83 } 84 } 85 86 /** 87 * Alias for {@link #delete(int)}. 88 */ 89 public void remove(int key) { 90 delete(key); 91 } 92 93 /** 94 * Removes the mapping at the specified index. 95 */ 96 public void removeAt(int index) { 97 if (mValues[index] != DELETED) { 98 mValues[index] = DELETED; 99 mGarbage = true; 100 } 101 } 102 103 private void gc() { 104 // Log.e("SparseArray", "gc start with " + mSize); 105 106 int n = mSize; 107 int o = 0; 108 int[] keys = mKeys; 109 Object[] values = mValues; 110 111 for (int i = 0; i < n; i++) { 112 Object val = values[i]; 113 114 if (val != DELETED) { 115 if (i != o) { 116 keys[o] = keys[i]; 117 values[o] = val; 118 } 119 120 o++; 121 } 122 } 123 124 mGarbage = false; 125 mSize = o; 126 127 // Log.e("SparseArray", "gc end with " + 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 */ 135 public void put(int key, E value) { 136 int i = binarySearch(mKeys, 0, mSize, key); 137 138 if (i >= 0) { 139 mValues[i] = value; 140 } else { 141 i = ~i; 142 143 if (i < mSize && mValues[i] == DELETED) { 144 mKeys[i] = key; 145 mValues[i] = value; 146 return; 147 } 148 149 if (mGarbage && mSize >= mKeys.length) { 150 gc(); 151 152 // Search again because indices may have changed. 153 i = ~binarySearch(mKeys, 0, mSize, key); 154 } 155 156 if (mSize >= mKeys.length) { 157 int n = ArrayUtils.idealIntArraySize(mSize + 1); 158 159 int[] nkeys = new int[n]; 160 Object[] nvalues = new Object[n]; 161 162 // Log.e("SparseArray", "grow " + mKeys.length + " to " + n); 163 System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length); 164 System.arraycopy(mValues, 0, nvalues, 0, mValues.length); 165 166 mKeys = nkeys; 167 mValues = nvalues; 168 } 169 170 if (mSize - i != 0) { 171 // Log.e("SparseArray", "move " + (mSize - i)); 172 System.arraycopy(mKeys, i, mKeys, i + 1, mSize - i); 173 System.arraycopy(mValues, i, mValues, i + 1, mSize - i); 174 } 175 176 mKeys[i] = key; 177 mValues[i] = value; 178 mSize++; 179 } 180 } 181 182 /** 183 * Returns the number of key-value mappings that this SparseArray 184 * currently stores. 185 */ 186 public int size() { 187 if (mGarbage) { 188 gc(); 189 } 190 191 return mSize; 192 } 193 194 /** 195 * Given an index in the range <code>0...size()-1</code>, returns 196 * the key from the <code>index</code>th key-value mapping that this 197 * SparseArray stores. 198 */ 199 public int keyAt(int index) { 200 if (mGarbage) { 201 gc(); 202 } 203 204 return mKeys[index]; 205 } 206 207 /** 208 * Given an index in the range <code>0...size()-1</code>, returns 209 * the value from the <code>index</code>th key-value mapping that this 210 * SparseArray stores. 211 */ 212 public E valueAt(int index) { 213 if (mGarbage) { 214 gc(); 215 } 216 217 return (E) mValues[index]; 218 } 219 220 /** 221 * Given an index in the range <code>0...size()-1</code>, sets a new 222 * value for the <code>index</code>th key-value mapping that this 223 * SparseArray stores. 224 */ 225 public void setValueAt(int index, E value) { 226 if (mGarbage) { 227 gc(); 228 } 229 230 mValues[index] = value; 231 } 232 233 /** 234 * Returns the index for which {@link #keyAt} would return the 235 * specified key, or a negative number if the specified 236 * key is not mapped. 237 */ 238 public int indexOfKey(int key) { 239 if (mGarbage) { 240 gc(); 241 } 242 243 return binarySearch(mKeys, 0, mSize, key); 244 } 245 246 /** 247 * Returns an index for which {@link #valueAt} would return the 248 * specified key, or a negative number if no keys map to the 249 * specified value. 250 * Beware that this is a linear search, unlike lookups by key, 251 * and that multiple keys can map to the same value and this will 252 * find only one of them. 253 */ 254 public int indexOfValue(E value) { 255 if (mGarbage) { 256 gc(); 257 } 258 259 for (int i = 0; i < mSize; i++) 260 if (mValues[i] == value) 261 return i; 262 263 return -1; 264 } 265 266 /** 267 * Removes all key-value mappings from this SparseArray. 268 */ 269 public void clear() { 270 int n = mSize; 271 Object[] values = mValues; 272 273 for (int i = 0; i < n; i++) { 274 values[i] = null; 275 } 276 277 mSize = 0; 278 mGarbage = false; 279 } 280 281 /** 282 * Puts a key/value pair into the array, optimizing for the case where 283 * the key is greater than all existing keys in the array. 284 */ 285 public void append(int key, E value) { 286 if (mSize != 0 && key <= mKeys[mSize - 1]) { 287 put(key, value); 288 return; 289 } 290 291 if (mGarbage && mSize >= mKeys.length) { 292 gc(); 293 } 294 295 int pos = mSize; 296 if (pos >= mKeys.length) { 297 int n = ArrayUtils.idealIntArraySize(pos + 1); 298 299 int[] nkeys = new int[n]; 300 Object[] nvalues = new Object[n]; 301 302 // Log.e("SparseArray", "grow " + mKeys.length + " to " + n); 303 System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length); 304 System.arraycopy(mValues, 0, nvalues, 0, mValues.length); 305 306 mKeys = nkeys; 307 mValues = nvalues; 308 } 309 310 mKeys[pos] = key; 311 mValues[pos] = value; 312 mSize = pos + 1; 313 } 314 315 private static int binarySearch(int[] a, int start, int len, int key) { 316 int high = start + len, low = start - 1, guess; 317 318 while (high - low > 1) { 319 guess = (high + low) / 2; 320 321 if (a[guess] < key) 322 low = guess; 323 else 324 high = guess; 325 } 326 327 if (high == start + len) 328 return ~(start + len); 329 else if (a[high] == key) 330 return high; 331 else 332 return ~high; 333 } 334 335 private void checkIntegrity() { 336 for (int i = 1; i < mSize; i++) { 337 if (mKeys[i] <= mKeys[i - 1]) { 338 for (int j = 0; j < mSize; j++) { 339 Log.e("FAIL", j + ": " + mKeys[j] + " -> " + mValues[j]); 340 } 341 342 throw new RuntimeException(); 343 } 344 } 345 } 346 347 private int[] mKeys; 348 private Object[] mValues; 349 private int mSize; 350} 351