1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. 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 /** 19 * @author Alexander Y. Kleymenov 20 */ 21 22 package libcore.io; 23 24 import java.nio.charset.StandardCharsets; 25 import libcore.util.EmptyArray; 26 27 /** 28 * <a href="http://www.ietf.org/rfc/rfc2045.txt">Base64</a> encoder/decoder. 29 * In violation of the RFC, this encoder doesn't wrap lines at 76 columns. 30 */ 31 public final class Base64 { 32 private Base64() { 33 } 34 35 public static byte[] decode(byte[] in) { 36 return decode(in, in.length); 37 } 38 39 public static byte[] decode(byte[] in, int len) { 40 // approximate output length 41 int length = len / 4 * 3; 42 // return an empty array on empty or short input without padding 43 if (length == 0) { 44 return EmptyArray.BYTE; 45 } 46 // temporary array 47 byte[] out = new byte[length]; 48 // number of padding characters ('=') 49 int pad = 0; 50 byte chr; 51 // compute the number of the padding characters 52 // and adjust the length of the input 53 for (;;len--) { 54 chr = in[len-1]; 55 // skip the neutral characters 56 if ((chr == '\n') || (chr == '\r') || 57 (chr == ' ') || (chr == '\t')) { 58 continue; 59 } 60 if (chr == '=') { 61 pad++; 62 } else { 63 break; 64 } 65 } 66 // index in the output array 67 int outIndex = 0; 68 // index in the input array 69 int inIndex = 0; 70 // holds the value of the input character 71 int bits = 0; 72 // holds the value of the input quantum 73 int quantum = 0; 74 for (int i=0; i<len; i++) { 75 chr = in[i]; 76 // skip the neutral characters 77 if ((chr == '\n') || (chr == '\r') || 78 (chr == ' ') || (chr == '\t')) { 79 continue; 80 } 81 if ((chr >= 'A') && (chr <= 'Z')) { 82 // char ASCII value 83 // A 65 0 84 // Z 90 25 (ASCII - 65) 85 bits = chr - 65; 86 } else if ((chr >= 'a') && (chr <= 'z')) { 87 // char ASCII value 88 // a 97 26 89 // z 122 51 (ASCII - 71) 90 bits = chr - 71; 91 } else if ((chr >= '0') && (chr <= '9')) { 92 // char ASCII value 93 // 0 48 52 94 // 9 57 61 (ASCII + 4) 95 bits = chr + 4; 96 } else if (chr == '+') { 97 bits = 62; 98 } else if (chr == '/') { 99 bits = 63; 100 } else { 101 return null; 102 } 103 // append the value to the quantum 104 quantum = (quantum << 6) | (byte) bits; 105 if (inIndex%4 == 3) { 106 // 4 characters were read, so make the output: 107 out[outIndex++] = (byte) (quantum >> 16); 108 out[outIndex++] = (byte) (quantum >> 8); 109 out[outIndex++] = (byte) quantum; 110 } 111 inIndex++; 112 } 113 if (pad > 0) { 114 // adjust the quantum value according to the padding 115 quantum = quantum << (6*pad); 116 // make output 117 out[outIndex++] = (byte) (quantum >> 16); 118 if (pad == 1) { 119 out[outIndex++] = (byte) (quantum >> 8); 120 } 121 } 122 // create the resulting array 123 byte[] result = new byte[outIndex]; 124 System.arraycopy(out, 0, result, 0, outIndex); 125 return result; 126 } 127 128 private static final byte[] map = new byte[] 129 {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 130 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 131 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 132 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', 133 '4', '5', '6', '7', '8', '9', '+', '/'}; 134 135 public static String encode(byte[] in) { 136 int length = (in.length + 2) * 4 / 3; 137 byte[] out = new byte[length]; 138 int index = 0, end = in.length - in.length % 3; 139 for (int i = 0; i < end; i += 3) { 140 out[index++] = map[(in[i] & 0xff) >> 2]; 141 out[index++] = map[((in[i] & 0x03) << 4) | ((in[i+1] & 0xff) >> 4)]; 142 out[index++] = map[((in[i+1] & 0x0f) << 2) | ((in[i+2] & 0xff) >> 6)]; 143 out[index++] = map[(in[i+2] & 0x3f)]; 144 } 145 switch (in.length % 3) { 146 case 1: 147 out[index++] = map[(in[end] & 0xff) >> 2]; 148 out[index++] = map[(in[end] & 0x03) << 4]; 149 out[index++] = '='; 150 out[index++] = '='; 151 break; 152 case 2: 153 out[index++] = map[(in[end] & 0xff) >> 2]; 154 out[index++] = map[((in[end] & 0x03) << 4) | ((in[end+1] & 0xff) >> 4)]; 155 out[index++] = map[((in[end+1] & 0x0f) << 2)]; 156 out[index++] = '='; 157 break; 158 } 159 return new String(out, 0, index, StandardCharsets.US_ASCII); 160 } 161 } 162
