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 com.android.dx.util;
18
19import java.io.UTFDataFormatException;
20
21/**
22 * Modified UTF-8 as described in the dex file format spec.
23 *
24 * <p>Derived from libcore's MUTF-8 encoder at java.nio.charset.ModifiedUtf8.
25 */
26public final class Mutf8 {
27    private Mutf8() {}
28
29    /**
30     * Decodes bytes from {@code in} into {@code out} until a delimiter 0x00 is
31     * encountered. Returns a new string containing the decoded characters.
32     */
33    public static String decode(ByteInput in, char[] out) throws UTFDataFormatException {
34        int s = 0;
35        while (true) {
36            char a = (char) (in.readByte() & 0xff);
37            if (a == 0) {
38                return new String(out, 0, s);
39            }
40            out[s] = a;
41            if (a < '\u0080') {
42                s++;
43            } else if ((a & 0xe0) == 0xc0) {
44                int b = in.readByte() & 0xff;
45                if ((b & 0xC0) != 0x80) {
46                    throw new UTFDataFormatException("bad second byte");
47                }
48                out[s++] = (char) (((a & 0x1F) << 6) | (b & 0x3F));
49            } else if ((a & 0xf0) == 0xe0) {
50                int b = in.readByte() & 0xff;
51                int c = in.readByte() & 0xff;
52                if (((b & 0xC0) != 0x80) || ((c & 0xC0) != 0x80)) {
53                    throw new UTFDataFormatException("bad second or third byte");
54                }
55                out[s++] = (char) (((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F));
56            } else {
57                throw new UTFDataFormatException("bad byte");
58            }
59        }
60    }
61
62    /**
63     * Returns the number of bytes the modified UTF8 representation of 's' would take.
64     */
65    private static long countBytes(String s, boolean shortLength) throws UTFDataFormatException {
66        long result = 0;
67        final int length = s.length();
68        for (int i = 0; i < length; ++i) {
69            char ch = s.charAt(i);
70            if (ch != 0 && ch <= 127) { // U+0000 uses two bytes.
71                ++result;
72            } else if (ch <= 2047) {
73                result += 2;
74            } else {
75                result += 3;
76            }
77            if (shortLength && result > 65535) {
78                throw new UTFDataFormatException("String more than 65535 UTF bytes long");
79            }
80        }
81        return result;
82    }
83
84    /**
85     * Encodes the modified UTF-8 bytes corresponding to {@code s} into  {@code
86     * dst}, starting at {@code offset}.
87     */
88    public static void encode(byte[] dst, int offset, String s) {
89        final int length = s.length();
90        for (int i = 0; i < length; i++) {
91            char ch = s.charAt(i);
92            if (ch != 0 && ch <= 127) { // U+0000 uses two bytes.
93                dst[offset++] = (byte) ch;
94            } else if (ch <= 2047) {
95                dst[offset++] = (byte) (0xc0 | (0x1f & (ch >> 6)));
96                dst[offset++] = (byte) (0x80 | (0x3f & ch));
97            } else {
98                dst[offset++] = (byte) (0xe0 | (0x0f & (ch >> 12)));
99                dst[offset++] = (byte) (0x80 | (0x3f & (ch >> 6)));
100                dst[offset++] = (byte) (0x80 | (0x3f & ch));
101            }
102        }
103    }
104
105    /**
106     * Returns an array containing the <i>modified UTF-8</i> form of {@code s}.
107     */
108    public static byte[] encode(String s) throws UTFDataFormatException {
109        int utfCount = (int) countBytes(s, true);
110        byte[] result = new byte[utfCount];
111        encode(result, 0, s);
112        return result;
113    }
114}
115