1/*
2 * Copyright (C) 2006 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;
20import com.android.internal.util.GrowingArrayUtils;
21
22import java.util.Arrays;
23
24import libcore.util.EmptyArray;
25
26/**
27 * SparseIntArrays map integers to integers.  Unlike a normal array of integers,
28 * there can be gaps in the indices.  It is intended to be more memory efficient
29 * than using a HashMap to map Integers to Integers, both because it avoids
30 * auto-boxing keys and values and its data structure doesn't rely on an extra entry object
31 * for each mapping.
32 *
33 * <p>Note that this container keeps its mappings in an array data structure,
34 * using a binary search to find keys.  The implementation is not intended to be appropriate for
35 * data structures
36 * that may contain large numbers of items.  It is generally slower than a traditional
37 * HashMap, since lookups require a binary search and adds and removes require inserting
38 * and deleting entries in the array.  For containers holding up to hundreds of items,
39 * the performance difference is not significant, less than 50%.</p>
40 *
41 * <p>It is possible to iterate over the items in this container using
42 * {@link #keyAt(int)} and {@link #valueAt(int)}. Iterating over the keys using
43 * <code>keyAt(int)</code> with ascending values of the index will return the
44 * keys in ascending order, or the values corresponding to the keys in ascending
45 * order in the case of <code>valueAt(int)</code>.</p>
46 */
47public class SparseIntArray implements Cloneable {
48    private int[] mKeys;
49    private int[] mValues;
50    private int mSize;
51
52    /**
53     * Creates a new SparseIntArray containing no mappings.
54     */
55    public SparseIntArray() {
56        this(10);
57    }
58
59    /**
60     * Creates a new SparseIntArray 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 SparseIntArray(int initialCapacity) {
67        if (initialCapacity == 0) {
68            mKeys = EmptyArray.INT;
69            mValues = EmptyArray.INT;
70        } else {
71            mKeys = ArrayUtils.newUnpaddedIntArray(initialCapacity);
72            mValues = new int[mKeys.length];
73        }
74        mSize = 0;
75    }
76
77    @Override
78    public SparseIntArray clone() {
79        SparseIntArray clone = null;
80        try {
81            clone = (SparseIntArray) 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 int mapped from the specified key, or <code>0</code>
92     * if no such mapping has been made.
93     */
94    public int get(int key) {
95        return get(key, 0);
96    }
97
98    /**
99     * Gets the int mapped from the specified key, or the specified value
100     * if no such mapping has been made.
101     */
102    public int get(int key, int 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(int 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(int key, int 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     * SparseIntArray 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 int 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     * SparseIntArray 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 int valueAt(int index) {
185        return mValues[index];
186    }
187
188    /**
189     * Directly set the value at a particular index.
190     * @hide
191     */
192    public void setValueAt(int index, int value) {
193        mValues[index] = value;
194    }
195
196    /**
197     * Returns the index for which {@link #keyAt} would return the
198     * specified key, or a negative number if the specified
199     * key is not mapped.
200     */
201    public int indexOfKey(int key) {
202        return ContainerHelpers.binarySearch(mKeys, mSize, key);
203    }
204
205    /**
206     * Returns an index for which {@link #valueAt} would return the
207     * specified key, or a negative number if no keys map to the
208     * specified value.
209     * Beware that this is a linear search, unlike lookups by key,
210     * and that multiple keys can map to the same value and this will
211     * find only one of them.
212     */
213    public int indexOfValue(int value) {
214        for (int i = 0; i < mSize; i++)
215            if (mValues[i] == value)
216                return i;
217
218        return -1;
219    }
220
221    /**
222     * Removes all key-value mappings from this SparseIntArray.
223     */
224    public void clear() {
225        mSize = 0;
226    }
227
228    /**
229     * Puts a key/value pair into the array, optimizing for the case where
230     * the key is greater than all existing keys in the array.
231     */
232    public void append(int key, int value) {
233        if (mSize != 0 && key <= mKeys[mSize - 1]) {
234            put(key, value);
235            return;
236        }
237
238        mKeys = GrowingArrayUtils.append(mKeys, mSize, key);
239        mValues = GrowingArrayUtils.append(mValues, mSize, value);
240        mSize++;
241    }
242
243    /**
244     * Provides a copy of keys.
245     *
246     * @hide
247     * */
248    public int[] copyKeys() {
249        if (size() == 0) {
250            return null;
251        }
252        return Arrays.copyOf(mKeys, size());
253    }
254
255    /**
256     * {@inheritDoc}
257     *
258     * <p>This implementation composes a string by iterating over its mappings.
259     */
260    @Override
261    public String toString() {
262        if (size() <= 0) {
263            return "{}";
264        }
265
266        StringBuilder buffer = new StringBuilder(mSize * 28);
267        buffer.append('{');
268        for (int i=0; i<mSize; i++) {
269            if (i > 0) {
270                buffer.append(", ");
271            }
272            int key = keyAt(i);
273            buffer.append(key);
274            buffer.append('=');
275            int value = valueAt(i);
276            buffer.append(value);
277        }
278        buffer.append('}');
279        return buffer.toString();
280    }
281}
282