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
17package android.util;
18
19import com.android.internal.util.ArrayUtils;
20import com.android.internal.util.GrowingArrayUtils;
21
22import 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 */
45public 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     */
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     */
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
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     */
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     */
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     */
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     * Removes the mapping at the given index.
123     */
124    public void removeAt(int index) {
125        System.arraycopy(mKeys, index + 1, mKeys, index, mSize - (index + 1));
126        System.arraycopy(mValues, index + 1, mValues, index, mSize - (index + 1));
127        mSize--;
128    }
129
130    /**
131     * Adds a mapping from the specified key to the specified value,
132     * replacing the previous mapping from the specified key if there
133     * was one.
134     */
135    public void put(int key, long value) {
136        int i = ContainerHelpers.binarySearch(mKeys, mSize, key);
137
138        if (i >= 0) {
139            mValues[i] = value;
140        } else {
141            i = ~i;
142
143            mKeys = GrowingArrayUtils.insert(mKeys, mSize, i, key);
144            mValues = GrowingArrayUtils.insert(mValues, mSize, i, value);
145            mSize++;
146        }
147    }
148
149    /**
150     * Returns the number of key-value mappings that this SparseIntArray
151     * currently stores.
152     */
153    public int size() {
154        return mSize;
155    }
156
157    /**
158     * Given an index in the range <code>0...size()-1</code>, returns
159     * the key from the <code>index</code>th key-value mapping that this
160     * SparseLongArray stores.
161     *
162     * <p>The keys corresponding to indices in ascending order are guaranteed to
163     * be in ascending order, e.g., <code>keyAt(0)</code> will return the
164     * smallest key and <code>keyAt(size()-1)</code> will return the largest
165     * key.</p>
166     */
167    public int 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     * <p>The values corresponding to indices in ascending order are guaranteed
177     * to be associated with keys in ascending order, e.g.,
178     * <code>valueAt(0)</code> will return the value associated with the
179     * smallest key and <code>valueAt(size()-1)</code> will return the value
180     * associated with the largest key.</p>
181     */
182    public long valueAt(int index) {
183        return mValues[index];
184    }
185
186    /**
187     * Returns the index for which {@link #keyAt} would return the
188     * specified key, or a negative number if the specified
189     * key is not mapped.
190     */
191    public int indexOfKey(int key) {
192        return ContainerHelpers.binarySearch(mKeys, mSize, key);
193    }
194
195    /**
196     * Returns an index for which {@link #valueAt} would return the
197     * specified key, or a negative number if no keys map to the
198     * specified value.
199     * Beware that this is a linear search, unlike lookups by key,
200     * and that multiple keys can map to the same value and this will
201     * find only one of them.
202     */
203    public int indexOfValue(long value) {
204        for (int i = 0; i < mSize; i++)
205            if (mValues[i] == value)
206                return i;
207
208        return -1;
209    }
210
211    /**
212     * Removes all key-value mappings from this SparseIntArray.
213     */
214    public void clear() {
215        mSize = 0;
216    }
217
218    /**
219     * Puts a key/value pair into the array, optimizing for the case where
220     * the key is greater than all existing keys in the array.
221     */
222    public void append(int key, long value) {
223        if (mSize != 0 && key <= mKeys[mSize - 1]) {
224            put(key, value);
225            return;
226        }
227
228        mKeys = GrowingArrayUtils.append(mKeys, mSize, key);
229        mValues = GrowingArrayUtils.append(mValues, mSize, value);
230        mSize++;
231    }
232
233    /**
234     * {@inheritDoc}
235     *
236     * <p>This implementation composes a string by iterating over its mappings.
237     */
238    @Override
239    public String toString() {
240        if (size() <= 0) {
241            return "{}";
242        }
243
244        StringBuilder buffer = new StringBuilder(mSize * 28);
245        buffer.append('{');
246        for (int i=0; i<mSize; i++) {
247            if (i > 0) {
248                buffer.append(", ");
249            }
250            int key = keyAt(i);
251            buffer.append(key);
252            buffer.append('=');
253            long value = valueAt(i);
254            buffer.append(value);
255        }
256        buffer.append('}');
257        return buffer.toString();
258    }
259}
260