1 /* 2 * Copyright (C) 2011 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 * SparseLongArrays map integers to longs. Unlike a normal array of longs, 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 Longs, 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 SparseLongArray implements Cloneable { 46 private int[] mKeys; 47 private long[] mValues; 48 private int mSize; 49 50 /** 51 * Creates a new SparseLongArray containing no mappings. 52 */ SparseLongArray()53 public SparseLongArray() { 54 this(10); 55 } 56 57 /** 58 * Creates a new SparseLongArray 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 */ SparseLongArray(int initialCapacity)64 public SparseLongArray(int initialCapacity) { 65 if (initialCapacity == 0) { 66 mKeys = EmptyArray.INT; 67 mValues = EmptyArray.LONG; 68 } else { 69 mValues = ArrayUtils.newUnpaddedLongArray(initialCapacity); 70 mKeys = new int[mValues.length]; 71 } 72 mSize = 0; 73 } 74 75 @Override clone()76 public SparseLongArray clone() { 77 SparseLongArray clone = null; 78 try { 79 clone = (SparseLongArray) 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 long mapped from the specified key, or <code>0</code> 90 * if no such mapping has been made. 91 */ get(int key)92 public long get(int key) { 93 return get(key, 0); 94 } 95 96 /** 97 * Gets the long mapped from the specified key, or the specified value 98 * if no such mapping has been made. 99 */ get(int key, long valueIfKeyNotFound)100 public long get(int key, long 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 * @hide 123 * Remove a range of mappings as a batch. 124 * 125 * @param index Index to begin at 126 * @param size Number of mappings to remove 127 * 128 * <p>For indices outside of the range <code>0...size()-1</code>, 129 * the behavior is undefined.</p> 130 */ removeAtRange(int index, int size)131 public void removeAtRange(int index, int size) { 132 size = Math.min(size, mSize - index); 133 System.arraycopy(mKeys, index + size, mKeys, index, mSize - (index + size)); 134 System.arraycopy(mValues, index + size, mValues, index, mSize - (index + size)); 135 mSize -= size; 136 } 137 138 /** 139 * Removes the mapping at the given index. 140 */ removeAt(int index)141 public void removeAt(int index) { 142 System.arraycopy(mKeys, index + 1, mKeys, index, mSize - (index + 1)); 143 System.arraycopy(mValues, index + 1, mValues, index, mSize - (index + 1)); 144 mSize--; 145 } 146 147 /** 148 * Adds a mapping from the specified key to the specified value, 149 * replacing the previous mapping from the specified key if there 150 * was one. 151 */ put(int key, long value)152 public void put(int key, long value) { 153 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 154 155 if (i >= 0) { 156 mValues[i] = value; 157 } else { 158 i = ~i; 159 160 mKeys = GrowingArrayUtils.insert(mKeys, mSize, i, key); 161 mValues = GrowingArrayUtils.insert(mValues, mSize, i, value); 162 mSize++; 163 } 164 } 165 166 /** 167 * Returns the number of key-value mappings that this SparseIntArray 168 * currently stores. 169 */ size()170 public int size() { 171 return mSize; 172 } 173 174 /** 175 * Given an index in the range <code>0...size()-1</code>, returns 176 * the key from the <code>index</code>th key-value mapping that this 177 * SparseLongArray stores. 178 * 179 * <p>The keys corresponding to indices in ascending order are guaranteed to 180 * be in ascending order, e.g., <code>keyAt(0)</code> will return the 181 * smallest key and <code>keyAt(size()-1)</code> will return the largest 182 * key.</p> 183 */ keyAt(int index)184 public int keyAt(int index) { 185 return mKeys[index]; 186 } 187 188 /** 189 * Given an index in the range <code>0...size()-1</code>, returns 190 * the value from the <code>index</code>th key-value mapping that this 191 * SparseLongArray stores. 192 * 193 * <p>The values corresponding to indices in ascending order are guaranteed 194 * to be associated with keys in ascending order, e.g., 195 * <code>valueAt(0)</code> will return the value associated with the 196 * smallest key and <code>valueAt(size()-1)</code> will return the value 197 * associated with the largest key.</p> 198 */ valueAt(int index)199 public long valueAt(int index) { 200 return mValues[index]; 201 } 202 203 /** 204 * Returns the index for which {@link #keyAt} would return the 205 * specified key, or a negative number if the specified 206 * key is not mapped. 207 */ indexOfKey(int key)208 public int indexOfKey(int key) { 209 return ContainerHelpers.binarySearch(mKeys, mSize, key); 210 } 211 212 /** 213 * Returns an index for which {@link #valueAt} would return the 214 * specified key, or a negative number if no keys map to the 215 * specified value. 216 * Beware that this is a linear search, unlike lookups by key, 217 * and that multiple keys can map to the same value and this will 218 * find only one of them. 219 */ indexOfValue(long value)220 public int indexOfValue(long value) { 221 for (int i = 0; i < mSize; i++) 222 if (mValues[i] == value) 223 return i; 224 225 return -1; 226 } 227 228 /** 229 * Removes all key-value mappings from this SparseIntArray. 230 */ clear()231 public void clear() { 232 mSize = 0; 233 } 234 235 /** 236 * Puts a key/value pair into the array, optimizing for the case where 237 * the key is greater than all existing keys in the array. 238 */ append(int key, long value)239 public void append(int key, long value) { 240 if (mSize != 0 && key <= mKeys[mSize - 1]) { 241 put(key, value); 242 return; 243 } 244 245 mKeys = GrowingArrayUtils.append(mKeys, mSize, key); 246 mValues = GrowingArrayUtils.append(mValues, mSize, value); 247 mSize++; 248 } 249 250 /** 251 * {@inheritDoc} 252 * 253 * <p>This implementation composes a string by iterating over its mappings. 254 */ 255 @Override toString()256 public String toString() { 257 if (size() <= 0) { 258 return "{}"; 259 } 260 261 StringBuilder buffer = new StringBuilder(mSize * 28); 262 buffer.append('{'); 263 for (int i=0; i<mSize; i++) { 264 if (i > 0) { 265 buffer.append(", "); 266 } 267 int key = keyAt(i); 268 buffer.append(key); 269 buffer.append('='); 270 long value = valueAt(i); 271 buffer.append(value); 272 } 273 buffer.append('}'); 274 return buffer.toString(); 275 } 276 } 277