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      */
LongSparseLongArray()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      */
LongSparseLongArray(int initialCapacity)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
clone()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      */
get(long key)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      */
get(long key, long valueIfKeyNotFound)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      */
delete(long key)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      */
removeAt(int index)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      */
put(long key, long value)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      */
size()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      */
keyAt(int index)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      */
valueAt(int index)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      */
indexOfKey(long key)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      */
indexOfValue(long value)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      */
clear()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      */
append(long key, long value)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
toString()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