LongSparseArray.java revision fdbf6a7eac39a23e0e910c29678fe00d4eb56c99
1/* 2 * Copyright (C) 2009 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 longs 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 Longs to Objects. 25 * 26 * @hide 27 */ 28public class LongSparseArray<E> { 29 private static final Object DELETED = new Object(); 30 private boolean mGarbage = false; 31 32 /** 33 * Creates a new SparseArray containing no mappings. 34 */ 35 public LongSparseArray() { 36 this(10); 37 } 38 39 /** 40 * Creates a new SparseArray containing no mappings that will not 41 * require any additional memory allocation to store the specified 42 * number of mappings. 43 */ 44 public LongSparseArray(int initialCapacity) { 45 initialCapacity = ArrayUtils.idealIntArraySize(initialCapacity); 46 47 mKeys = new long[initialCapacity]; 48 mValues = new Object[initialCapacity]; 49 mSize = 0; 50 } 51 52 /** 53 * Gets the Object mapped from the specified key, or <code>null</code> 54 * if no such mapping has been made. 55 */ 56 public E get(long key) { 57 return get(key, null); 58 } 59 60 /** 61 * Gets the Object mapped from the specified key, or the specified Object 62 * if no such mapping has been made. 63 */ 64 public E get(long key, E valueIfKeyNotFound) { 65 int i = binarySearch(mKeys, 0, mSize, key); 66 67 if (i < 0 || mValues[i] == DELETED) { 68 return valueIfKeyNotFound; 69 } else { 70 return (E) mValues[i]; 71 } 72 } 73 74 /** 75 * Removes the mapping from the specified key, if there was any. 76 */ 77 public void delete(long key) { 78 int i = binarySearch(mKeys, 0, mSize, key); 79 80 if (i >= 0) { 81 if (mValues[i] != DELETED) { 82 mValues[i] = DELETED; 83 mGarbage = true; 84 } 85 } 86 } 87 88 /** 89 * Alias for {@link #delete(long)}. 90 */ 91 public void remove(long key) { 92 delete(key); 93 } 94 95 private void gc() { 96 // Log.e("SparseArray", "gc start with " + mSize); 97 98 int n = mSize; 99 int o = 0; 100 long[] keys = mKeys; 101 Object[] values = mValues; 102 103 for (int i = 0; i < n; i++) { 104 Object val = values[i]; 105 106 if (val != DELETED) { 107 if (i != o) { 108 keys[o] = keys[i]; 109 values[o] = val; 110 } 111 112 o++; 113 } 114 } 115 116 mGarbage = false; 117 mSize = o; 118 119 // Log.e("SparseArray", "gc end with " + mSize); 120 } 121 122 /** 123 * Adds a mapping from the specified key to the specified value, 124 * replacing the previous mapping from the specified key if there 125 * was one. 126 */ 127 public void put(long key, E value) { 128 int i = binarySearch(mKeys, 0, mSize, key); 129 130 if (i >= 0) { 131 mValues[i] = value; 132 } else { 133 i = ~i; 134 135 if (i < mSize && mValues[i] == DELETED) { 136 mKeys[i] = key; 137 mValues[i] = value; 138 return; 139 } 140 141 if (mGarbage && mSize >= mKeys.length) { 142 gc(); 143 144 // Search again because indices may have changed. 145 i = ~binarySearch(mKeys, 0, mSize, key); 146 } 147 148 if (mSize >= mKeys.length) { 149 int n = ArrayUtils.idealIntArraySize(mSize + 1); 150 151 long[] nkeys = new long[n]; 152 Object[] nvalues = new Object[n]; 153 154 // Log.e("SparseArray", "grow " + mKeys.length + " to " + n); 155 System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length); 156 System.arraycopy(mValues, 0, nvalues, 0, mValues.length); 157 158 mKeys = nkeys; 159 mValues = nvalues; 160 } 161 162 if (mSize - i != 0) { 163 // Log.e("SparseArray", "move " + (mSize - i)); 164 System.arraycopy(mKeys, i, mKeys, i + 1, mSize - i); 165 System.arraycopy(mValues, i, mValues, i + 1, mSize - i); 166 } 167 168 mKeys[i] = key; 169 mValues[i] = value; 170 mSize++; 171 } 172 } 173 174 /** 175 * Returns the number of key-value mappings that this SparseArray 176 * currently stores. 177 */ 178 public int size() { 179 if (mGarbage) { 180 gc(); 181 } 182 183 return mSize; 184 } 185 186 /** 187 * Given an index in the range <code>0...size()-1</code>, returns 188 * the key from the <code>index</code>th key-value mapping that this 189 * SparseArray stores. 190 */ 191 public long keyAt(int index) { 192 if (mGarbage) { 193 gc(); 194 } 195 196 return mKeys[index]; 197 } 198 199 /** 200 * Given an index in the range <code>0...size()-1</code>, returns 201 * the value from the <code>index</code>th key-value mapping that this 202 * SparseArray stores. 203 */ 204 public E valueAt(int index) { 205 if (mGarbage) { 206 gc(); 207 } 208 209 return (E) mValues[index]; 210 } 211 212 /** 213 * Given an index in the range <code>0...size()-1</code>, sets a new 214 * value for the <code>index</code>th key-value mapping that this 215 * SparseArray stores. 216 */ 217 public void setValueAt(int index, E value) { 218 if (mGarbage) { 219 gc(); 220 } 221 222 mValues[index] = value; 223 } 224 225 /** 226 * Returns the index for which {@link #keyAt} would return the 227 * specified key, or a negative number if the specified 228 * key is not mapped. 229 */ 230 public int indexOfKey(long key) { 231 if (mGarbage) { 232 gc(); 233 } 234 235 return binarySearch(mKeys, 0, mSize, key); 236 } 237 238 /** 239 * Returns an index for which {@link #valueAt} would return the 240 * specified key, or a negative number if no keys map to the 241 * specified value. 242 * Beware that this is a linear search, unlike lookups by key, 243 * and that multiple keys can map to the same value and this will 244 * find only one of them. 245 */ 246 public int indexOfValue(E value) { 247 if (mGarbage) { 248 gc(); 249 } 250 251 for (int i = 0; i < mSize; i++) 252 if (mValues[i] == value) 253 return i; 254 255 return -1; 256 } 257 258 /** 259 * Removes all key-value mappings from this SparseArray. 260 */ 261 public void clear() { 262 int n = mSize; 263 Object[] values = mValues; 264 265 for (int i = 0; i < n; i++) { 266 values[i] = null; 267 } 268 269 mSize = 0; 270 mGarbage = false; 271 } 272 273 /** 274 * Puts a key/value pair into the array, optimizing for the case where 275 * the key is greater than all existing keys in the array. 276 */ 277 public void append(long key, E value) { 278 if (mSize != 0 && key <= mKeys[mSize - 1]) { 279 put(key, value); 280 return; 281 } 282 283 if (mGarbage && mSize >= mKeys.length) { 284 gc(); 285 } 286 287 int pos = mSize; 288 if (pos >= mKeys.length) { 289 int n = ArrayUtils.idealIntArraySize(pos + 1); 290 291 long[] nkeys = new long[n]; 292 Object[] nvalues = new Object[n]; 293 294 // Log.e("SparseArray", "grow " + mKeys.length + " to " + n); 295 System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length); 296 System.arraycopy(mValues, 0, nvalues, 0, mValues.length); 297 298 mKeys = nkeys; 299 mValues = nvalues; 300 } 301 302 mKeys[pos] = key; 303 mValues[pos] = value; 304 mSize = pos + 1; 305 } 306 307 private static int binarySearch(long[] a, int start, int len, long key) { 308 int high = start + len, low = start - 1, guess; 309 310 while (high - low > 1) { 311 guess = (high + low) / 2; 312 313 if (a[guess] < key) 314 low = guess; 315 else 316 high = guess; 317 } 318 319 if (high == start + len) 320 return ~(start + len); 321 else if (a[high] == key) 322 return high; 323 else 324 return ~high; 325 } 326 327 private void checkIntegrity() { 328 for (int i = 1; i < mSize; i++) { 329 if (mKeys[i] <= mKeys[i - 1]) { 330 for (int j = 0; j < mSize; j++) { 331 Log.e("FAIL", j + ": " + mKeys[j] + " -> " + mValues[j]); 332 } 333 334 throw new RuntimeException(); 335 } 336 } 337 } 338 339 private long[] mKeys; 340 private Object[] mValues; 341 private int mSize; 342}