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 com.android.internal.util;
18
19import java.lang.reflect.Array;
20
21// XXX these should be changed to reflect the actual memory allocator we use.
22// it looks like right now objects want to be powers of 2 minus 8
23// and the array size eats another 4 bytes
24
25/**
26 * ArrayUtils contains some methods that you can call to find out
27 * the most efficient increments by which to grow arrays.
28 */
29public class ArrayUtils
30{
31    private static Object[] EMPTY = new Object[0];
32    private static final int CACHE_SIZE = 73;
33    private static Object[] sCache = new Object[CACHE_SIZE];
34
35    private ArrayUtils() { /* cannot be instantiated */ }
36
37    public static int idealByteArraySize(int need) {
38        for (int i = 4; i < 32; i++)
39            if (need <= (1 << i) - 12)
40                return (1 << i) - 12;
41
42        return need;
43    }
44
45    public static int idealBooleanArraySize(int need) {
46        return idealByteArraySize(need);
47    }
48
49    public static int idealShortArraySize(int need) {
50        return idealByteArraySize(need * 2) / 2;
51    }
52
53    public static int idealCharArraySize(int need) {
54        return idealByteArraySize(need * 2) / 2;
55    }
56
57    public static int idealIntArraySize(int need) {
58        return idealByteArraySize(need * 4) / 4;
59    }
60
61    public static int idealFloatArraySize(int need) {
62        return idealByteArraySize(need * 4) / 4;
63    }
64
65    public static int idealObjectArraySize(int need) {
66        return idealByteArraySize(need * 4) / 4;
67    }
68
69    public static int idealLongArraySize(int need) {
70        return idealByteArraySize(need * 8) / 8;
71    }
72
73    /**
74     * Checks if the beginnings of two byte arrays are equal.
75     *
76     * @param array1 the first byte array
77     * @param array2 the second byte array
78     * @param length the number of bytes to check
79     * @return true if they're equal, false otherwise
80     */
81    public static boolean equals(byte[] array1, byte[] array2, int length) {
82        if (array1 == array2) {
83            return true;
84        }
85        if (array1 == null || array2 == null || array1.length < length || array2.length < length) {
86            return false;
87        }
88        for (int i = 0; i < length; i++) {
89            if (array1[i] != array2[i]) {
90                return false;
91            }
92        }
93        return true;
94    }
95
96    /**
97     * Returns an empty array of the specified type.  The intent is that
98     * it will return the same empty array every time to avoid reallocation,
99     * although this is not guaranteed.
100     */
101    public static <T> T[] emptyArray(Class<T> kind) {
102        if (kind == Object.class) {
103            return (T[]) EMPTY;
104        }
105
106        int bucket = ((System.identityHashCode(kind) / 8) & 0x7FFFFFFF) % CACHE_SIZE;
107        Object cache = sCache[bucket];
108
109        if (cache == null || cache.getClass().getComponentType() != kind) {
110            cache = Array.newInstance(kind, 0);
111            sCache[bucket] = cache;
112
113            // Log.e("cache", "new empty " + kind.getName() + " at " + bucket);
114        }
115
116        return (T[]) cache;
117    }
118
119    /**
120     * Checks that value is present as at least one of the elements of the array.
121     * @param array the array to check in
122     * @param value the value to check for
123     * @return true if the value is present in the array
124     */
125    public static <T> boolean contains(T[] array, T value) {
126        for (T element : array) {
127            if (element == null) {
128                if (value == null) return true;
129            } else {
130                if (value != null && element.equals(value)) return true;
131            }
132        }
133        return false;
134    }
135
136    public static boolean contains(int[] array, int value) {
137        for (int element : array) {
138            if (element == value) {
139                return true;
140            }
141        }
142        return false;
143    }
144
145    public static long total(long[] array) {
146        long total = 0;
147        for (long value : array) {
148            total += value;
149        }
150        return total;
151    }
152
153    /**
154     * Appends an element to a copy of the array and returns the copy.
155     * @param array The original array, or null to represent an empty array.
156     * @param element The element to add.
157     * @return A new array that contains all of the elements of the original array
158     * with the specified element added at the end.
159     */
160    @SuppressWarnings("unchecked")
161    public static <T> T[] appendElement(Class<T> kind, T[] array, T element) {
162        final T[] result;
163        final int end;
164        if (array != null) {
165            end = array.length;
166            result = (T[])Array.newInstance(kind, end + 1);
167            System.arraycopy(array, 0, result, 0, end);
168        } else {
169            end = 0;
170            result = (T[])Array.newInstance(kind, 1);
171        }
172        result[end] = element;
173        return result;
174    }
175
176    /**
177     * Removes an element from a copy of the array and returns the copy.
178     * If the element is not present, then the original array is returned unmodified.
179     * @param array The original array, or null to represent an empty array.
180     * @param element The element to remove.
181     * @return A new array that contains all of the elements of the original array
182     * except the first copy of the specified element removed.  If the specified element
183     * was not present, then returns the original array.  Returns null if the result
184     * would be an empty array.
185     */
186    @SuppressWarnings("unchecked")
187    public static <T> T[] removeElement(Class<T> kind, T[] array, T element) {
188        if (array != null) {
189            final int length = array.length;
190            for (int i = 0; i < length; i++) {
191                if (array[i] == element) {
192                    if (length == 1) {
193                        return null;
194                    }
195                    T[] result = (T[])Array.newInstance(kind, length - 1);
196                    System.arraycopy(array, 0, result, 0, i);
197                    System.arraycopy(array, i + 1, result, i, length - i - 1);
198                    return result;
199                }
200            }
201        }
202        return array;
203    }
204
205    public static int[] appendInt(int[] cur, int val) {
206        if (cur == null) {
207            return new int[] { val };
208        }
209        final int N = cur.length;
210        for (int i = 0; i < N; i++) {
211            if (cur[i] == val) {
212                return cur;
213            }
214        }
215        int[] ret = new int[N + 1];
216        System.arraycopy(cur, 0, ret, 0, N);
217        ret[N] = val;
218        return ret;
219    }
220
221    public static int[] removeInt(int[] cur, int val) {
222        if (cur == null) {
223            return null;
224        }
225        final int N = cur.length;
226        for (int i = 0; i < N; i++) {
227            if (cur[i] == val) {
228                int[] ret = new int[N - 1];
229                if (i > 0) {
230                    System.arraycopy(cur, 0, ret, 0, i);
231                }
232                if (i < (N - 1)) {
233                    System.arraycopy(cur, i + 1, ret, i, N - i - 1);
234                }
235                return ret;
236            }
237        }
238        return cur;
239    }
240}
241