[120] | 1 | /* |
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| 2 | * @(#)Base64.java 1.4 03/01/23 |
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| 3 | * |
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| 4 | * Copyright 2003 Sun Microsystems, Inc. All rights reserved. |
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| 5 | * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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| 6 | */ |
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| 7 | |
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| 8 | /** |
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| 9 | * Static methods for translating Base64 encoded strings to byte arrays |
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| 10 | * and vice-versa. |
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| 11 | * |
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| 12 | * @author Josh Bloch |
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| 13 | * @version 1.4, 01/23/03 |
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| 14 | * @see Preferences |
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| 15 | * @since 1.4 |
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| 16 | */ |
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| 17 | public class Base64 { |
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| 18 | /** |
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| 19 | * Translates the specified byte array into a Base64 string as per |
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| 20 | * Preferences.put(byte[]). |
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| 21 | */ |
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| 22 | static String byteArrayToBase64(byte[] a) { |
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| 23 | return byteArrayToBase64(a, false); |
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| 24 | } |
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| 25 | |
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| 26 | /** |
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| 27 | * Translates the specified byte array into an "aternate representation" |
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| 28 | * Base64 string. This non-standard variant uses an alphabet that does |
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| 29 | * not contain the uppercase alphabetic characters, which makes it |
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| 30 | * suitable for use in situations where case-folding occurs. |
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| 31 | */ |
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| 32 | static String byteArrayToAltBase64(byte[] a) { |
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| 33 | return byteArrayToBase64(a, true); |
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| 34 | } |
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| 35 | |
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| 36 | private static String byteArrayToBase64(byte[] a, boolean alternate) { |
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| 37 | int aLen = a.length; |
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| 38 | int numFullGroups = aLen/3; |
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| 39 | int numBytesInPartialGroup = aLen - 3*numFullGroups; |
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| 40 | int resultLen = 4*((aLen + 2)/3); |
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| 41 | StringBuffer result = new StringBuffer(resultLen); |
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| 42 | char[] intToAlpha = (alternate ? intToAltBase64 : intToBase64); |
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| 43 | |
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| 44 | // Translate all full groups from byte array elements to Base64 |
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| 45 | int inCursor = 0; |
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| 46 | for (int i=0; i<numFullGroups; i++) { |
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| 47 | int byte0 = a[inCursor++] & 0xff; |
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| 48 | int byte1 = a[inCursor++] & 0xff; |
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| 49 | int byte2 = a[inCursor++] & 0xff; |
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| 50 | result.append(intToAlpha[byte0 >> 2]); |
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| 51 | result.append(intToAlpha[(byte0 << 4)&0x3f | (byte1 >> 4)]); |
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| 52 | result.append(intToAlpha[(byte1 << 2)&0x3f | (byte2 >> 6)]); |
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| 53 | result.append(intToAlpha[byte2 & 0x3f]); |
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| 54 | } |
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| 55 | |
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| 56 | // Translate partial group if present |
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| 57 | if (numBytesInPartialGroup != 0) { |
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| 58 | int byte0 = a[inCursor++] & 0xff; |
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| 59 | result.append(intToAlpha[byte0 >> 2]); |
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| 60 | if (numBytesInPartialGroup == 1) { |
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| 61 | result.append(intToAlpha[(byte0 << 4) & 0x3f]); |
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| 62 | result.append("=="); |
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| 63 | } else { |
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| 64 | // assert numBytesInPartialGroup == 2; |
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| 65 | int byte1 = a[inCursor++] & 0xff; |
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| 66 | result.append(intToAlpha[(byte0 << 4)&0x3f | (byte1 >> 4)]); |
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| 67 | result.append(intToAlpha[(byte1 << 2)&0x3f]); |
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| 68 | result.append('='); |
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| 69 | } |
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| 70 | } |
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| 71 | // assert inCursor == a.length; |
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| 72 | // assert result.length() == resultLen; |
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| 73 | return result.toString(); |
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| 74 | } |
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| 75 | |
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| 76 | /** |
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| 77 | * This array is a lookup table that translates 6-bit positive integer |
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| 78 | * index values into their "Base64 Alphabet" equivalents as specified |
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| 79 | * in Table 1 of RFC 2045. |
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| 80 | */ |
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| 81 | private static final char intToBase64[] = { |
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| 82 | 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', |
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| 83 | 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', |
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| 84 | 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', |
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| 85 | 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', |
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| 86 | '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' |
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| 87 | }; |
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| 88 | |
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| 89 | /** |
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| 90 | * This array is a lookup table that translates 6-bit positive integer |
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| 91 | * index values into their "Alternate Base64 Alphabet" equivalents. |
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| 92 | * This is NOT the real Base64 Alphabet as per in Table 1 of RFC 2045. |
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| 93 | * This alternate alphabet does not use the capital letters. It is |
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| 94 | * designed for use in environments where "case folding" occurs. |
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| 95 | */ |
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| 96 | private static final char intToAltBase64[] = { |
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| 97 | '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':', |
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| 98 | ';', '<', '>', '@', '[', ']', '^', '`', '_', '{', '|', '}', '~', |
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| 99 | 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', |
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| 100 | 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', |
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| 101 | '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '?' |
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| 102 | }; |
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| 103 | |
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| 104 | /** |
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| 105 | * Translates the specified Base64 string (as per Preferences.get(byte[])) |
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| 106 | * into a byte array. |
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| 107 | * |
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| 108 | * @throw IllegalArgumentException if <tt>s</tt> is not a valid Base64 |
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| 109 | * string. |
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| 110 | */ |
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| 111 | static byte[] base64ToByteArray(String s) { |
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| 112 | return base64ToByteArray(s, false); |
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| 113 | } |
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| 114 | |
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| 115 | /** |
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| 116 | * Translates the specified "aternate representation" Base64 string |
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| 117 | * into a byte array. |
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| 118 | * |
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| 119 | * @throw IllegalArgumentException or ArrayOutOfBoundsException |
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| 120 | * if <tt>s</tt> is not a valid alternate representation |
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| 121 | * Base64 string. |
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| 122 | */ |
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| 123 | static byte[] altBase64ToByteArray(String s) { |
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| 124 | return base64ToByteArray(s, true); |
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| 125 | } |
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| 126 | |
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| 127 | private static byte[] base64ToByteArray(String s, boolean alternate) { |
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| 128 | byte[] alphaToInt = (alternate ? altBase64ToInt : base64ToInt); |
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| 129 | int sLen = s.length(); |
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| 130 | int numGroups = sLen/4; |
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| 131 | if (4*numGroups != sLen) |
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| 132 | throw new IllegalArgumentException( |
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| 133 | "String length must be a multiple of four."); |
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| 134 | int missingBytesInLastGroup = 0; |
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| 135 | int numFullGroups = numGroups; |
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| 136 | if (sLen != 0) { |
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| 137 | if (s.charAt(sLen-1) == '=') { |
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| 138 | missingBytesInLastGroup++; |
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| 139 | numFullGroups--; |
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| 140 | } |
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| 141 | if (s.charAt(sLen-2) == '=') |
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| 142 | missingBytesInLastGroup++; |
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| 143 | } |
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| 144 | byte[] result = new byte[3*numGroups - missingBytesInLastGroup]; |
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| 145 | |
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| 146 | // Translate all full groups from base64 to byte array elements |
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| 147 | int inCursor = 0, outCursor = 0; |
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| 148 | for (int i=0; i<numFullGroups; i++) { |
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| 149 | int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt); |
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| 150 | int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt); |
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| 151 | int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt); |
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| 152 | int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt); |
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| 153 | result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4)); |
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| 154 | result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2)); |
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| 155 | result[outCursor++] = (byte) ((ch2 << 6) | ch3); |
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| 156 | } |
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| 157 | |
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| 158 | // Translate partial group, if present |
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| 159 | if (missingBytesInLastGroup != 0) { |
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| 160 | int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt); |
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| 161 | int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt); |
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| 162 | result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4)); |
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| 163 | |
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| 164 | if (missingBytesInLastGroup == 1) { |
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| 165 | int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt); |
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| 166 | result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2)); |
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| 167 | } |
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| 168 | } |
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| 169 | // assert inCursor == s.length()-missingBytesInLastGroup; |
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| 170 | // assert outCursor == result.length; |
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| 171 | return result; |
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| 172 | } |
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| 173 | |
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| 174 | /** |
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| 175 | * Translates the specified character, which is assumed to be in the |
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| 176 | * "Base 64 Alphabet" into its equivalent 6-bit positive integer. |
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| 177 | * |
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| 178 | * @throw IllegalArgumentException or ArrayOutOfBoundsException if |
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| 179 | * c is not in the Base64 Alphabet. |
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| 180 | */ |
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| 181 | private static int base64toInt(char c, byte[] alphaToInt) { |
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| 182 | int result = alphaToInt[c]; |
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| 183 | if (result < 0) |
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| 184 | throw new IllegalArgumentException("Illegal character " + c); |
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| 185 | return result; |
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| 186 | } |
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| 187 | |
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| 188 | /** |
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| 189 | * This array is a lookup table that translates unicode characters |
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| 190 | * drawn from the "Base64 Alphabet" (as specified in Table 1 of RFC 2045) |
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| 191 | * into their 6-bit positive integer equivalents. Characters that |
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| 192 | * are not in the Base64 alphabet but fall within the bounds of the |
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| 193 | * array are translated to -1. |
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| 194 | */ |
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| 195 | private static final byte base64ToInt[] = { |
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| 196 | -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, |
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| 197 | -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, |
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| 198 | -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, |
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| 199 | 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, |
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| 200 | 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, |
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| 201 | 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, |
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| 202 | 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 |
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| 203 | }; |
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| 204 | |
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| 205 | /** |
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| 206 | * This array is the analogue of base64ToInt, but for the nonstandard |
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| 207 | * variant that avoids the use of uppercase alphabetic characters. |
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| 208 | */ |
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| 209 | private static final byte altBase64ToInt[] = { |
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| 210 | -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, |
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| 211 | -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, |
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| 212 | 2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10, 11, -1 , 52, 53, 54, 55, 56, 57, |
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| 213 | 58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1, |
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| 214 | -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, |
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| 215 | -1, -1, -1, 17, -1, 18, 19, 21, 20, 26, 27, 28, 29, 30, 31, 32, 33, |
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| 216 | 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, |
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| 217 | 51, 22, 23, 24, 25 |
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| 218 | }; |
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| 219 | } |
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