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 
18 package com.example.android.mmslib.pdu;
19 
20 import java.io.ByteArrayOutputStream;
21 
22 public 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      */
decodeQuotedPrintable(byte[] bytes)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