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
17package com.android.internal.util;
18
19/**
20 * {@link CharSequence} utility methods.
21 */
22public class CharSequences {
23
24    /**
25     * Adapts {@link CharSequence} to an array of ASCII (7-bits per character)
26     * bytes.
27     *
28     * @param bytes ASCII bytes
29     */
30    public static CharSequence forAsciiBytes(final byte[] bytes) {
31        return new CharSequence() {
32            public char charAt(int index) {
33                return (char) bytes[index];
34            }
35
36            public int length() {
37                return bytes.length;
38            }
39
40            public CharSequence subSequence(int start, int end) {
41                return forAsciiBytes(bytes, start, end);
42            }
43
44            public String toString() {
45                return new String(bytes);
46            }
47        };
48    }
49
50    /**
51     * Adapts {@link CharSequence} to an array of ASCII (7-bits per character)
52     * bytes.
53     *
54     * @param bytes ASCII bytes
55     * @param start index, inclusive
56     * @param end index, exclusive
57     *
58     * @throws IndexOutOfBoundsException if start or end are negative, if end
59     *  is greater than length(), or if start is greater than end
60     */
61    public static CharSequence forAsciiBytes(final byte[] bytes,
62            final int start, final int end) {
63        validate(start, end, bytes.length);
64        return new CharSequence() {
65            public char charAt(int index) {
66                return (char) bytes[index + start];
67            }
68
69            public int length() {
70                return end - start;
71            }
72
73            public CharSequence subSequence(int newStart, int newEnd) {
74                newStart -= start;
75                newEnd -= start;
76                validate(newStart, newEnd, length());
77                return forAsciiBytes(bytes, newStart, newEnd);
78            }
79
80            public String toString() {
81                return new String(bytes, start, length());
82            }
83        };
84    }
85
86    static void validate(int start, int end, int length) {
87        if (start < 0) throw new IndexOutOfBoundsException();
88        if (end < 0) throw new IndexOutOfBoundsException();
89        if (end > length) throw new IndexOutOfBoundsException();
90        if (start > end) throw new IndexOutOfBoundsException();
91    }
92
93    /**
94     * Compares two character sequences for equality.
95     */
96    public static boolean equals(CharSequence a, CharSequence b) {
97        if (a.length() != b.length()) {
98            return false;
99        }
100
101        int length = a.length();
102        for (int i = 0; i < length; i++) {
103            if (a.charAt(i) != b.charAt(i)) {
104                return false;
105            }
106        }
107        return true;
108    }
109
110    /**
111     * Compares two character sequences with API like {@link Comparable#compareTo}.
112     *
113     * @param me The CharSequence that receives the compareTo call.
114     * @param another The other CharSequence.
115     * @return See {@link Comparable#compareTo}.
116     */
117    public static int compareToIgnoreCase(CharSequence me, CharSequence another) {
118        // Code adapted from String#compareTo
119        int myLen = me.length(), anotherLen = another.length();
120        int myPos = 0, anotherPos = 0, result;
121        int end = (myLen < anotherLen) ? myLen : anotherLen;
122
123        while (myPos < end) {
124            if ((result = Character.toLowerCase(me.charAt(myPos++))
125                    - Character.toLowerCase(another.charAt(anotherPos++))) != 0) {
126                return result;
127            }
128        }
129        return myLen - anotherLen;
130    }
131}
132