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.google.android.mms.pdu;
19 
20 import android.compat.annotation.UnsupportedAppUsage;
21 
22 import java.io.ByteArrayOutputStream;
23 
24 public class QuotedPrintable {
25     private static byte ESCAPE_CHAR = '=';
26 
27     /**
28      * Decodes an array quoted-printable characters into an array of original bytes.
29      * Escaped characters are converted back to their original representation.
30      *
31      * <p>
32      * This function implements a subset of
33      * quoted-printable encoding specification (rule #1 and rule #2)
34      * as defined in RFC 1521.
35      * </p>
36      *
37      * @param bytes array of quoted-printable characters
38      * @return array of original bytes,
39      *         null if quoted-printable decoding is unsuccessful.
40      */
41     @UnsupportedAppUsage
decodeQuotedPrintable(byte[] bytes)42     public static final byte[] decodeQuotedPrintable(byte[] bytes) {
43         if (bytes == null) {
44             return null;
45         }
46         ByteArrayOutputStream buffer = new ByteArrayOutputStream();
47         for (int i = 0; i < bytes.length; i++) {
48             int b = bytes[i];
49             if (b == ESCAPE_CHAR) {
50                 try {
51                     if('\r' == (char)bytes[i + 1] &&
52                             '\n' == (char)bytes[i + 2]) {
53                         i += 2;
54                         continue;
55                     }
56                     int u = Character.digit((char) bytes[++i], 16);
57                     int l = Character.digit((char) bytes[++i], 16);
58                     if (u == -1 || l == -1) {
59                         return null;
60                     }
61                     buffer.write((char) ((u << 4) + l));
62                 } catch (ArrayIndexOutOfBoundsException e) {
63                     return null;
64                 }
65             } else {
66                 buffer.write(b);
67             }
68         }
69         return buffer.toByteArray();
70     }
71 }
72