1 /* 2 * Copyright (C) 2007 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 * Map of {@code long} to {@code long}. Unlike a normal array of longs, there 26 * can be gaps in the indices. It is intended to be more memory efficient than using a 27 * {@code HashMap}, 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 * @hide 46 */ 47 public class LongSparseLongArray implements Cloneable { 48 private long[] mKeys; 49 private long[] mValues; 50 private int mSize; 51 52 /** 53 * Creates a new SparseLongArray containing no mappings. 54 */ 55 public LongSparseLongArray() { 56 this(10); 57 } 58 59 /** 60 * Creates a new SparseLongArray containing no mappings that will not 61 * require any additional memory allocation to store the specified 62 * number of mappings. If you supply an initial capacity of 0, the 63 * sparse array will be initialized with a light-weight representation 64 * not requiring any additional array allocations. 65 */ 66 public LongSparseLongArray(int initialCapacity) { 67 if (initialCapacity == 0) { 68 mKeys = EmptyArray.LONG; 69 mValues = EmptyArray.LONG; 70 } else { 71 mKeys = ArrayUtils.newUnpaddedLongArray(initialCapacity); 72 mValues = new long[mKeys.length]; 73 } 74 mSize = 0; 75 } 76 77 @Override 78 public LongSparseLongArray clone() { 79 LongSparseLongArray clone = null; 80 try { 81 clone = (LongSparseLongArray) super.clone(); 82 clone.mKeys = mKeys.clone(); 83 clone.mValues = mValues.clone(); 84 } catch (CloneNotSupportedException cnse) { 85 /* ignore */ 86 } 87 return clone; 88 } 89 90 /** 91 * Gets the long mapped from the specified key, or <code>0</code> 92 * if no such mapping has been made. 93 */ 94 public long get(long key) { 95 return get(key, 0); 96 } 97 98 /** 99 * Gets the long mapped from the specified key, or the specified value 100 * if no such mapping has been made. 101 */ 102 public long get(long key, long valueIfKeyNotFound) { 103 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 104 105 if (i < 0) { 106 return valueIfKeyNotFound; 107 } else { 108 return mValues[i]; 109 } 110 } 111 112 /** 113 * Removes the mapping from the specified key, if there was any. 114 */ 115 public void delete(long key) { 116 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 117 118 if (i >= 0) { 119 removeAt(i); 120 } 121 } 122 123 /** 124 * Removes the mapping at the given index. 125 */ 126 public void removeAt(int index) { 127 System.arraycopy(mKeys, index + 1, mKeys, index, mSize - (index + 1)); 128 System.arraycopy(mValues, index + 1, mValues, index, mSize - (index + 1)); 129 mSize--; 130 } 131 132 /** 133 * Adds a mapping from the specified key to the specified value, 134 * replacing the previous mapping from the specified key if there 135 * was one. 136 */ 137 public void put(long key, long value) { 138 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 139 140 if (i >= 0) { 141 mValues[i] = value; 142 } else { 143 i = ~i; 144 145 mKeys = GrowingArrayUtils.insert(mKeys, mSize, i, key); 146 mValues = GrowingArrayUtils.insert(mValues, mSize, i, value); 147 mSize++; 148 } 149 } 150 151 /** 152 * Returns the number of key-value mappings that this SparseIntArray 153 * currently stores. 154 */ 155 public int size() { 156 return mSize; 157 } 158 159 /** 160 * Given an index in the range <code>0...size()-1</code>, returns 161 * the key from the <code>index</code>th key-value mapping that this 162 * SparseLongArray stores. 163 * 164 * <p>The keys corresponding to indices in ascending order are guaranteed to 165 * be in ascending order, e.g., <code>keyAt(0)</code> will return the 166 * smallest key and <code>keyAt(size()-1)</code> will return the largest 167 * key.</p> 168 */ 169 public long keyAt(int index) { 170 return mKeys[index]; 171 } 172 173 /** 174 * Given an index in the range <code>0...size()-1</code>, returns 175 * the value from the <code>index</code>th key-value mapping that this 176 * SparseLongArray stores. 177 * 178 * <p>The values corresponding to indices in ascending order are guaranteed 179 * to be associated with keys in ascending order, e.g., 180 * <code>valueAt(0)</code> will return the value associated with the 181 * smallest key and <code>valueAt(size()-1)</code> will return the value 182 * associated with the largest key.</p> 183 */ 184 public long valueAt(int index) { 185 return mValues[index]; 186 } 187 188 /** 189 * Returns the index for which {@link #keyAt} would return the 190 * specified key, or a negative number if the specified 191 * key is not mapped. 192 */ 193 public int indexOfKey(long key) { 194 return ContainerHelpers.binarySearch(mKeys, mSize, key); 195 } 196 197 /** 198 * Returns an index for which {@link #valueAt} would return the 199 * specified key, or a negative number if no keys map to the 200 * specified value. 201 * Beware that this is a linear search, unlike lookups by key, 202 * and that multiple keys can map to the same value and this will 203 * find only one of them. 204 */ 205 public int indexOfValue(long value) { 206 for (int i = 0; i < mSize; i++) 207 if (mValues[i] == value) 208 return i; 209 210 return -1; 211 } 212 213 /** 214 * Removes all key-value mappings from this SparseIntArray. 215 */ 216 public void clear() { 217 mSize = 0; 218 } 219 220 /** 221 * Puts a key/value pair into the array, optimizing for the case where 222 * the key is greater than all existing keys in the array. 223 */ 224 public void append(long key, long value) { 225 if (mSize != 0 && key <= mKeys[mSize - 1]) { 226 put(key, value); 227 return; 228 } 229 230 mKeys = GrowingArrayUtils.append(mKeys, mSize, key); 231 mValues = GrowingArrayUtils.append(mValues, mSize, value); 232 mSize++; 233 } 234 235 /** 236 * {@inheritDoc} 237 * 238 * <p>This implementation composes a string by iterating over its mappings. 239 */ 240 @Override 241 public String toString() { 242 if (size() <= 0) { 243 return "{}"; 244 } 245 246 StringBuilder buffer = new StringBuilder(mSize * 28); 247 buffer.append('{'); 248 for (int i=0; i<mSize; i++) { 249 if (i > 0) { 250 buffer.append(", "); 251 } 252 long key = keyAt(i); 253 buffer.append(key); 254 buffer.append('='); 255 long value = valueAt(i); 256 buffer.append(value); 257 } 258 buffer.append('}'); 259 return buffer.toString(); 260 } 261 } 262
