The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 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 | |
Tom Taylor | 5e342fa | 2010-01-28 15:54:15 -0800 | [diff] [blame^] | 18 | package com.android.mmscommon.mms.pdu; |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 19 | |
| 20 | public class Base64 { |
| 21 | /** |
| 22 | * Used to get the number of Quadruples. |
| 23 | */ |
| 24 | static final int FOURBYTE = 4; |
| 25 | |
| 26 | /** |
| 27 | * Byte used to pad output. |
| 28 | */ |
| 29 | static final byte PAD = (byte) '='; |
| 30 | |
| 31 | /** |
| 32 | * The base length. |
| 33 | */ |
| 34 | static final int BASELENGTH = 255; |
| 35 | |
| 36 | // Create arrays to hold the base64 characters |
| 37 | private static byte[] base64Alphabet = new byte[BASELENGTH]; |
| 38 | |
| 39 | // Populating the character arrays |
| 40 | static { |
| 41 | for (int i = 0; i < BASELENGTH; i++) { |
| 42 | base64Alphabet[i] = (byte) -1; |
| 43 | } |
| 44 | for (int i = 'Z'; i >= 'A'; i--) { |
| 45 | base64Alphabet[i] = (byte) (i - 'A'); |
| 46 | } |
| 47 | for (int i = 'z'; i >= 'a'; i--) { |
| 48 | base64Alphabet[i] = (byte) (i - 'a' + 26); |
| 49 | } |
| 50 | for (int i = '9'; i >= '0'; i--) { |
| 51 | base64Alphabet[i] = (byte) (i - '0' + 52); |
| 52 | } |
| 53 | |
| 54 | base64Alphabet['+'] = 62; |
| 55 | base64Alphabet['/'] = 63; |
| 56 | } |
| 57 | |
| 58 | /** |
| 59 | * Decodes Base64 data into octects |
| 60 | * |
| 61 | * @param base64Data Byte array containing Base64 data |
| 62 | * @return Array containing decoded data. |
| 63 | */ |
| 64 | public static byte[] decodeBase64(byte[] base64Data) { |
| 65 | // RFC 2045 requires that we discard ALL non-Base64 characters |
| 66 | base64Data = discardNonBase64(base64Data); |
| 67 | |
| 68 | // handle the edge case, so we don't have to worry about it later |
| 69 | if (base64Data.length == 0) { |
| 70 | return new byte[0]; |
| 71 | } |
| 72 | |
| 73 | int numberQuadruple = base64Data.length / FOURBYTE; |
| 74 | byte decodedData[] = null; |
| 75 | byte b1 = 0, b2 = 0, b3 = 0, b4 = 0, marker0 = 0, marker1 = 0; |
| 76 | |
| 77 | // Throw away anything not in base64Data |
| 78 | |
| 79 | int encodedIndex = 0; |
| 80 | int dataIndex = 0; |
| 81 | { |
| 82 | // this sizes the output array properly - rlw |
| 83 | int lastData = base64Data.length; |
| 84 | // ignore the '=' padding |
| 85 | while (base64Data[lastData - 1] == PAD) { |
| 86 | if (--lastData == 0) { |
| 87 | return new byte[0]; |
| 88 | } |
| 89 | } |
| 90 | decodedData = new byte[lastData - numberQuadruple]; |
| 91 | } |
| 92 | |
| 93 | for (int i = 0; i < numberQuadruple; i++) { |
| 94 | dataIndex = i * 4; |
| 95 | marker0 = base64Data[dataIndex + 2]; |
| 96 | marker1 = base64Data[dataIndex + 3]; |
| 97 | |
| 98 | b1 = base64Alphabet[base64Data[dataIndex]]; |
| 99 | b2 = base64Alphabet[base64Data[dataIndex + 1]]; |
| 100 | |
| 101 | if (marker0 != PAD && marker1 != PAD) { |
| 102 | //No PAD e.g 3cQl |
| 103 | b3 = base64Alphabet[marker0]; |
| 104 | b4 = base64Alphabet[marker1]; |
| 105 | |
| 106 | decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4); |
| 107 | decodedData[encodedIndex + 1] = |
| 108 | (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf)); |
| 109 | decodedData[encodedIndex + 2] = (byte) (b3 << 6 | b4); |
| 110 | } else if (marker0 == PAD) { |
| 111 | //Two PAD e.g. 3c[Pad][Pad] |
| 112 | decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4); |
| 113 | } else if (marker1 == PAD) { |
| 114 | //One PAD e.g. 3cQ[Pad] |
| 115 | b3 = base64Alphabet[marker0]; |
| 116 | |
| 117 | decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4); |
| 118 | decodedData[encodedIndex + 1] = |
| 119 | (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf)); |
| 120 | } |
| 121 | encodedIndex += 3; |
| 122 | } |
| 123 | return decodedData; |
| 124 | } |
| 125 | |
| 126 | /** |
| 127 | * Check octect wheter it is a base64 encoding. |
| 128 | * |
| 129 | * @param octect to be checked byte |
| 130 | * @return ture if it is base64 encoding, false otherwise. |
| 131 | */ |
| 132 | private static boolean isBase64(byte octect) { |
| 133 | if (octect == PAD) { |
| 134 | return true; |
| 135 | } else if (base64Alphabet[octect] == -1) { |
| 136 | return false; |
| 137 | } else { |
| 138 | return true; |
| 139 | } |
| 140 | } |
| 141 | |
| 142 | /** |
| 143 | * Discards any characters outside of the base64 alphabet, per |
| 144 | * the requirements on page 25 of RFC 2045 - "Any characters |
| 145 | * outside of the base64 alphabet are to be ignored in base64 |
| 146 | * encoded data." |
| 147 | * |
| 148 | * @param data The base-64 encoded data to groom |
| 149 | * @return The data, less non-base64 characters (see RFC 2045). |
| 150 | */ |
| 151 | static byte[] discardNonBase64(byte[] data) { |
| 152 | byte groomedData[] = new byte[data.length]; |
| 153 | int bytesCopied = 0; |
| 154 | |
| 155 | for (int i = 0; i < data.length; i++) { |
| 156 | if (isBase64(data[i])) { |
| 157 | groomedData[bytesCopied++] = data[i]; |
| 158 | } |
| 159 | } |
| 160 | |
| 161 | byte packedData[] = new byte[bytesCopied]; |
| 162 | |
| 163 | System.arraycopy(groomedData, 0, packedData, 0, bytesCopied); |
| 164 | |
| 165 | return packedData; |
| 166 | } |
| 167 | } |