ArrayUtils.java revision 3a44f3f1b446315ef894e01d2ab9b5388c2bd8c4 
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 dalvik.system.VMRuntime;
20import libcore.util.EmptyArray;
21
22import java.lang.reflect.Array;
23
24/**
25 * ArrayUtils contains some methods that you can call to find out
26 * the most efficient increments by which to grow arrays.
27 */
28public class ArrayUtils
29{
30    private static final int CACHE_SIZE = 73;
31    private static Object[] sCache = new Object[CACHE_SIZE];
32
33    private ArrayUtils() { /* cannot be instantiated */ }
34
35    public static byte[] newUnpaddedByteArray(int minLen) {
36        return (byte[])VMRuntime.getRuntime().newUnpaddedArray(byte.class, minLen);
37    }
38
39    public static char[] newUnpaddedCharArray(int minLen) {
40        return (char[])VMRuntime.getRuntime().newUnpaddedArray(char.class, minLen);
41    }
42
43    public static int[] newUnpaddedIntArray(int minLen) {
44        return (int[])VMRuntime.getRuntime().newUnpaddedArray(int.class, minLen);
45    }
46
47    public static boolean[] newUnpaddedBooleanArray(int minLen) {
48        return (boolean[])VMRuntime.getRuntime().newUnpaddedArray(boolean.class, minLen);
49    }
50
51    public static long[] newUnpaddedLongArray(int minLen) {
52        return (long[])VMRuntime.getRuntime().newUnpaddedArray(long.class, minLen);
53    }
54
55    public static float[] newUnpaddedFloatArray(int minLen) {
56        return (float[])VMRuntime.getRuntime().newUnpaddedArray(float.class, minLen);
57    }
58
59    public static Object[] newUnpaddedObjectArray(int minLen) {
60        return (Object[])VMRuntime.getRuntime().newUnpaddedArray(Object.class, minLen);
61    }
62
63    @SuppressWarnings("unchecked")
64    public static <T> T[] newUnpaddedArray(Class<T> clazz, int minLen) {
65        return (T[])VMRuntime.getRuntime().newUnpaddedArray(clazz, minLen);
66    }
67
68    /**
69     * Checks if the beginnings of two byte arrays are equal.
70     *
71     * @param array1 the first byte array
72     * @param array2 the second byte array
73     * @param length the number of bytes to check
74     * @return true if they're equal, false otherwise
75     */
76    public static boolean equals(byte[] array1, byte[] array2, int length) {
77        if (length < 0) {
78            throw new IllegalArgumentException();
79        }
80
81        if (array1 == array2) {
82            return true;
83        }
84        if (array1 == null || array2 == null || array1.length < length || array2.length < length) {
85            return false;
86        }
87        for (int i = 0; i < length; i++) {
88            if (array1[i] != array2[i]) {
89                return false;
90            }
91        }
92        return true;
93    }
94
95    /**
96     * Returns an empty array of the specified type.  The intent is that
97     * it will return the same empty array every time to avoid reallocation,
98     * although this is not guaranteed.
99     */
100    @SuppressWarnings("unchecked")
101    public static <T> T[] emptyArray(Class<T> kind) {
102        if (kind == Object.class) {
103            return (T[]) EmptyArray.OBJECT;
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 if given array is null or has zero elements.
121     */
122    public static <T> boolean isEmpty(T[] array) {
123        return array == null || array.length == 0;
124    }
125
126    /**
127     * Checks that value is present as at least one of the elements of the array.
128     * @param array the array to check in
129     * @param value the value to check for
130     * @return true if the value is present in the array
131     */
132    public static <T> boolean contains(T[] array, T value) {
133        return indexOf(array, value) != -1;
134    }
135
136    /**
137     * Return first index of {@code value} in {@code array}, or {@code -1} if
138     * not found.
139     */
140    public static <T> int indexOf(T[] array, T value) {
141        for (int i = 0; i < array.length; i++) {
142            if (array[i] == null) {
143                if (value == null) return i;
144            } else {
145                if (value != null && array[i].equals(value)) return i;
146            }
147        }
148        return -1;
149    }
150
151    /**
152     * Test if all {@code check} items are contained in {@code array}.
153     */
154    public static <T> boolean containsAll(T[] array, T[] check) {
155        for (T checkItem : check) {
156            if (!contains(array, checkItem)) {
157                return false;
158            }
159        }
160        return true;
161    }
162
163    public static boolean contains(int[] array, int value) {
164        for (int element : array) {
165            if (element == value) {
166                return true;
167            }
168        }
169        return false;
170    }
171
172    public static long total(long[] array) {
173        long total = 0;
174        for (long value : array) {
175            total += value;
176        }
177        return total;
178    }
179
180    /**
181     * Appends an element to a copy of the array and returns the copy.
182     * @param array The original array, or null to represent an empty array.
183     * @param element The element to add.
184     * @return A new array that contains all of the elements of the original array
185     * with the specified element added at the end.
186     */
187    @SuppressWarnings("unchecked")
188    public static <T> T[] appendElement(Class<T> kind, T[] array, T element) {
189        final T[] result;
190        final int end;
191        if (array != null) {
192            end = array.length;
193            result = (T[])Array.newInstance(kind, end + 1);
194            System.arraycopy(array, 0, result, 0, end);
195        } else {
196            end = 0;
197            result = (T[])Array.newInstance(kind, 1);
198        }
199        result[end] = element;
200        return result;
201    }
202
203    /**
204     * Removes an element from a copy of the array and returns the copy.
205     * If the element is not present, then the original array is returned unmodified.
206     * @param array The original array, or null to represent an empty array.
207     * @param element The element to remove.
208     * @return A new array that contains all of the elements of the original array
209     * except the first copy of the specified element removed.  If the specified element
210     * was not present, then returns the original array.  Returns null if the result
211     * would be an empty array.
212     */
213    @SuppressWarnings("unchecked")
214    public static <T> T[] removeElement(Class<T> kind, T[] array, T element) {
215        if (array != null) {
216            final int length = array.length;
217            for (int i = 0; i < length; i++) {
218                if (array[i] == element) {
219                    if (length == 1) {
220                        return null;
221                    }
222                    T[] result = (T[])Array.newInstance(kind, length - 1);
223                    System.arraycopy(array, 0, result, 0, i);
224                    System.arraycopy(array, i + 1, result, i, length - i - 1);
225                    return result;
226                }
227            }
228        }
229        return array;
230    }
231
232    public static int[] appendInt(int[] cur, int val) {
233        if (cur == null) {
234            return new int[] { val };
235        }
236        final int N = cur.length;
237        for (int i = 0; i < N; i++) {
238            if (cur[i] == val) {
239                return cur;
240            }
241        }
242        int[] ret = new int[N + 1];
243        System.arraycopy(cur, 0, ret, 0, N);
244        ret[N] = val;
245        return ret;
246    }
247
248    public static int[] removeInt(int[] cur, int val) {
249        if (cur == null) {
250            return null;
251        }
252        final int N = cur.length;
253        for (int i = 0; i < N; i++) {
254            if (cur[i] == val) {
255                int[] ret = new int[N - 1];
256                if (i > 0) {
257                    System.arraycopy(cur, 0, ret, 0, i);
258                }
259                if (i < (N - 1)) {
260                    System.arraycopy(cur, i + 1, ret, i, N - i - 1);
261                }
262                return ret;
263            }
264        }
265        return cur;
266    }
267}
268