The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 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 | * 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 | */ |
| 26 | public 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 | |
Dianne Hackborn | c801768 | 2010-07-06 13:34:38 -0700 | [diff] [blame] | 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 | |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 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 | } |