LongSparseLongArray.java revision 3e82ba1a67b0c756ab6a289985f4cfc53725b311
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 17package android.util; 18 19import com.android.internal.util.ArrayUtils; 20 21import java.util.Arrays; 22 23/** 24 * Map of {@code long} to {@code long}. Unlike a normal array of longs, there 25 * can be gaps in the indices. It is intended to be more memory efficient than using a 26 * {@code HashMap}, both because it avoids 27 * auto-boxing keys and values and its data structure doesn't rely on an extra entry object 28 * for each mapping. 29 * 30 * <p>Note that this container keeps its mappings in an array data structure, 31 * using a binary search to find keys. The implementation is not intended to be appropriate for 32 * data structures 33 * that may contain large numbers of items. It is generally slower than a traditional 34 * HashMap, since lookups require a binary search and adds and removes require inserting 35 * and deleting entries in the array. For containers holding up to hundreds of items, 36 * the performance difference is not significant, less than 50%.</p> 37 * 38 * @hide 39 */ 40public class LongSparseLongArray implements Cloneable { 41 private long[] mKeys; 42 private long[] mValues; 43 private int mSize; 44 45 /** 46 * Creates a new SparseLongArray containing no mappings. 47 */ 48 public LongSparseLongArray() { 49 this(10); 50 } 51 52 /** 53 * Creates a new SparseLongArray containing no mappings that will not 54 * require any additional memory allocation to store the specified 55 * number of mappings. If you supply an initial capacity of 0, the 56 * sparse array will be initialized with a light-weight representation 57 * not requiring any additional array allocations. 58 */ 59 public LongSparseLongArray(int initialCapacity) { 60 if (initialCapacity == 0) { 61 mKeys = ContainerHelpers.EMPTY_LONGS; 62 mValues = ContainerHelpers.EMPTY_LONGS; 63 } else { 64 initialCapacity = ArrayUtils.idealLongArraySize(initialCapacity); 65 mKeys = new long[initialCapacity]; 66 mValues = new long[initialCapacity]; 67 } 68 mSize = 0; 69 } 70 71 @Override 72 public LongSparseLongArray clone() { 73 LongSparseLongArray clone = null; 74 try { 75 clone = (LongSparseLongArray) super.clone(); 76 clone.mKeys = mKeys.clone(); 77 clone.mValues = mValues.clone(); 78 } catch (CloneNotSupportedException cnse) { 79 /* ignore */ 80 } 81 return clone; 82 } 83 84 /** 85 * Gets the long mapped from the specified key, or <code>0</code> 86 * if no such mapping has been made. 87 */ 88 public long get(long key) { 89 return get(key, 0); 90 } 91 92 /** 93 * Gets the long mapped from the specified key, or the specified value 94 * if no such mapping has been made. 95 */ 96 public long get(long key, long valueIfKeyNotFound) { 97 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 98 99 if (i < 0) { 100 return valueIfKeyNotFound; 101 } else { 102 return mValues[i]; 103 } 104 } 105 106 /** 107 * Removes the mapping from the specified key, if there was any. 108 */ 109 public void delete(long key) { 110 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 111 112 if (i >= 0) { 113 removeAt(i); 114 } 115 } 116 117 /** 118 * Removes the mapping at the given index. 119 */ 120 public void removeAt(int index) { 121 System.arraycopy(mKeys, index + 1, mKeys, index, mSize - (index + 1)); 122 System.arraycopy(mValues, index + 1, mValues, index, mSize - (index + 1)); 123 mSize--; 124 } 125 126 /** 127 * Adds a mapping from the specified key to the specified value, 128 * replacing the previous mapping from the specified key if there 129 * was one. 130 */ 131 public void put(long key, long value) { 132 int i = ContainerHelpers.binarySearch(mKeys, mSize, key); 133 134 if (i >= 0) { 135 mValues[i] = value; 136 } else { 137 i = ~i; 138 139 if (mSize >= mKeys.length) { 140 growKeyAndValueArrays(mSize + 1); 141 } 142 143 if (mSize - i != 0) { 144 System.arraycopy(mKeys, i, mKeys, i + 1, mSize - i); 145 System.arraycopy(mValues, i, mValues, i + 1, mSize - i); 146 } 147 148 mKeys[i] = key; 149 mValues[i] = value; 150 mSize++; 151 } 152 } 153 154 /** 155 * Returns the number of key-value mappings that this SparseIntArray 156 * currently stores. 157 */ 158 public int size() { 159 return mSize; 160 } 161 162 /** 163 * Given an index in the range <code>0...size()-1</code>, returns 164 * the key from the <code>index</code>th key-value mapping that this 165 * SparseLongArray stores. 166 */ 167 public long keyAt(int index) { 168 return mKeys[index]; 169 } 170 171 /** 172 * Given an index in the range <code>0...size()-1</code>, returns 173 * the value from the <code>index</code>th key-value mapping that this 174 * SparseLongArray stores. 175 */ 176 public long valueAt(int index) { 177 return mValues[index]; 178 } 179 180 /** 181 * Returns the index for which {@link #keyAt} would return the 182 * specified key, or a negative number if the specified 183 * key is not mapped. 184 */ 185 public int indexOfKey(long key) { 186 return ContainerHelpers.binarySearch(mKeys, mSize, key); 187 } 188 189 /** 190 * Returns an index for which {@link #valueAt} would return the 191 * specified key, or a negative number if no keys map to the 192 * specified value. 193 * Beware that this is a linear search, unlike lookups by key, 194 * and that multiple keys can map to the same value and this will 195 * find only one of them. 196 */ 197 public int indexOfValue(long value) { 198 for (int i = 0; i < mSize; i++) 199 if (mValues[i] == value) 200 return i; 201 202 return -1; 203 } 204 205 /** 206 * Removes all key-value mappings from this SparseIntArray. 207 */ 208 public void clear() { 209 mSize = 0; 210 } 211 212 /** 213 * Puts a key/value pair into the array, optimizing for the case where 214 * the key is greater than all existing keys in the array. 215 */ 216 public void append(long key, long value) { 217 if (mSize != 0 && key <= mKeys[mSize - 1]) { 218 put(key, value); 219 return; 220 } 221 222 int pos = mSize; 223 if (pos >= mKeys.length) { 224 growKeyAndValueArrays(pos + 1); 225 } 226 227 mKeys[pos] = key; 228 mValues[pos] = value; 229 mSize = pos + 1; 230 } 231 232 private void growKeyAndValueArrays(int minNeededSize) { 233 int n = ArrayUtils.idealLongArraySize(minNeededSize); 234 235 long[] nkeys = new long[n]; 236 long[] nvalues = new long[n]; 237 238 System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length); 239 System.arraycopy(mValues, 0, nvalues, 0, mValues.length); 240 241 mKeys = nkeys; 242 mValues = nvalues; 243 } 244 245 /** 246 * {@inheritDoc} 247 * 248 * <p>This implementation composes a string by iterating over its mappings. 249 */ 250 @Override 251 public String toString() { 252 if (size() <= 0) { 253 return "{}"; 254 } 255 256 StringBuilder buffer = new StringBuilder(mSize * 28); 257 buffer.append('{'); 258 for (int i=0; i<mSize; i++) { 259 if (i > 0) { 260 buffer.append(", "); 261 } 262 long key = keyAt(i); 263 buffer.append(key); 264 buffer.append('='); 265 long value = valueAt(i); 266 buffer.append(value); 267 } 268 buffer.append('}'); 269 return buffer.toString(); 270 } 271} 272