1/*
2 * Copyright (C) 2007 Esmertec AG.
3 * Copyright (C) 2007 The Android Open Source Project
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 *      http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18package com.google.android.mms.pdu;
19
20import java.io.ByteArrayOutputStream;
21
22public class QuotedPrintable {
23    private static byte ESCAPE_CHAR = '=';
24
25    /**
26     * Decodes an array quoted-printable characters into an array of original bytes.
27     * Escaped characters are converted back to their original representation.
28     *
29     * <p>
30     * This function implements a subset of
31     * quoted-printable encoding specification (rule #1 and rule #2)
32     * as defined in RFC 1521.
33     * </p>
34     *
35     * @param bytes array of quoted-printable characters
36     * @return array of original bytes,
37     *         null if quoted-printable decoding is unsuccessful.
38     */
39    public static final byte[] decodeQuotedPrintable(byte[] bytes) {
40        if (bytes == null) {
41            return null;
42        }
43        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
44        for (int i = 0; i < bytes.length; i++) {
45            int b = bytes[i];
46            if (b == ESCAPE_CHAR) {
47                try {
48                    if('\r' == (char)bytes[i + 1] &&
49                            '\n' == (char)bytes[i + 2]) {
50                        i += 2;
51                        continue;
52                    }
53                    int u = Character.digit((char) bytes[++i], 16);
54                    int l = Character.digit((char) bytes[++i], 16);
55                    if (u == -1 || l == -1) {
56                        return null;
57                    }
58                    buffer.write((char) ((u << 4) + l));
59                } catch (ArrayIndexOutOfBoundsException e) {
60                    return null;
61                }
62            } else {
63                buffer.write(b);
64            }
65        }
66        return buffer.toByteArray();
67    }
68}
69