1. /*

  2.  * @(#)Base64.java	1.5 03/12/19

  3.  *

  4.  * Copyright 2004 Sun Microsystems, Inc. All rights reserved.

  5.  * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.

  6.  */

  7. 

  8. package java.util.prefs;

  9. 

  10. /**

  11.  * Static methods for translating Base64 encoded strings to byte arrays

  12.  * and vice-versa.

  13.  *

  14.  * @author  Josh Bloch

  15.  * @version 1.5, 12/19/03

  16.  * @see     Preferences

  17.  * @since   1.4

  18.  */

  19. class Base64 {

  20.     /**

  21.      * Translates the specified byte array into a Base64 string as per

  22.      * Preferences.put(byte[]).

  23.      */

  24.     static String byteArrayToBase64(byte[] a) {

  25.         return byteArrayToBase64(a, false);

  26.     }

  27. 

  28.     /**

  29.      * Translates the specified byte array into an "aternate representation"

  30.      * Base64 string.  This non-standard variant uses an alphabet that does

  31.      * not contain the uppercase alphabetic characters, which makes it

  32.      * suitable for use in situations where case-folding occurs.

  33.      */

  34.     static String byteArrayToAltBase64(byte[] a) {

  35.         return byteArrayToBase64(a, true);

  36.     }

  37. 

  38.     private static String byteArrayToBase64(byte[] a, boolean alternate) {

  39.         int aLen = a.length;

  40.         int numFullGroups = aLen3;

  41.         int numBytesInPartialGroup = aLen - 3*numFullGroups;

  42.         int resultLen = 4*((aLen + 2)/3);

  43.         StringBuffer result = new StringBuffer(resultLen);

  44.         char[] intToAlpha = (alternate ? intToAltBase64 : intToBase64);

  45. 

  46.         // Translate all full groups from byte array elements to Base64

  47.         int inCursor = 0;

  48.         for (int i=0; i<numFullGroups; i++) {

  49.             int byte0 = a[inCursor++] & 0xff;

  50.             int byte1 = a[inCursor++] & 0xff;

  51.             int byte2 = a[inCursor++] & 0xff;

  52.             result.append(intToAlpha[byte0 >> 2]);

  53.             result.append(intToAlpha[(byte0 << 4)&0x3f | (byte1 >> 4)]);

  54.             result.append(intToAlpha[(byte1 << 2)&0x3f | (byte2 >> 6)]);

  55.             result.append(intToAlpha[byte2 & 0x3f]);

  56.         }

  57. 

  58.         // Translate partial group if present

  59.         if (numBytesInPartialGroup != 0) {

  60.             int byte0 = a[inCursor++] & 0xff;

  61.             result.append(intToAlpha[byte0 >> 2]);

  62.             if (numBytesInPartialGroup == 1) {

  63.                 result.append(intToAlpha[(byte0 << 4) & 0x3f]);

  64.                 result.append("==");

  65.             } else {

  66.                 // assert numBytesInPartialGroup == 2;

  67.                 int byte1 = a[inCursor++] & 0xff;

  68.                 result.append(intToAlpha[(byte0 << 4)&0x3f | (byte1 >> 4)]);

  69.                 result.append(intToAlpha[(byte1 << 2)&0x3f]);

  70.                 result.append('=');

  71.             }

  72.         }

  73.         // assert inCursor == a.length;

  74.         // assert result.length() == resultLen;

  75.         return result.toString();

  76.     }

  77. 

  78.     /**

  79.      * This array is a lookup table that translates 6-bit positive integer

  80.      * index values into their "Base64 Alphabet" equivalents as specified 

  81.      * in Table 1 of RFC 2045.

  82.      */

  83.     private static final char intToBase64[] = {

  84.         'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',

  85.         'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',

  86.         'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',

  87.         'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',

  88.         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'

  89.     };

  90. 

  91.     /**

  92.      * This array is a lookup table that translates 6-bit positive integer

  93.      * index values into their "Alternate Base64 Alphabet" equivalents.

  94.      * This is NOT the real Base64 Alphabet as per in Table 1 of RFC 2045.

  95.      * This alternate alphabet does not use the capital letters.  It is

  96.      * designed for use in environments where "case folding" occurs.

  97.      */

  98.     private static final char intToAltBase64[] = {

  99.         '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':',

  100.         ';', '<', '>', '@', '[', ']', '^',  '`', '_', '{', '|', '}', '~',

  101.         'a', 'b', 'c', 'd', 'e', 'f', 'g',  'h', 'i', 'j', 'k', 'l', 'm',

  102.         'n', 'o', 'p', 'q', 'r', 's', 't',  'u', 'v', 'w', 'x', 'y', 'z',

  103.         '0', '1', '2', '3', '4', '5', '6',  '7', '8', '9', '+', '?'

  104.     };

  105. 

  106.     /**

  107.      * Translates the specified Base64 string (as per Preferences.get(byte[]))

  108.      * into a byte array.

  109.      * 

  110.      * @throw IllegalArgumentException if <tt>s</tt> is not a valid Base64

  111.      *        string.

  112.      */

  113.     static byte[] base64ToByteArray(String s) {

  114.         return base64ToByteArray(s, false);

  115.     }

  116. 

  117.     /**

  118.      * Translates the specified "aternate representation" Base64 string

  119.      * into a byte array.

  120.      * 

  121.      * @throw IllegalArgumentException or ArrayOutOfBoundsException

  122.      *        if <tt>s</tt> is not a valid alternate representation

  123.      *        Base64 string.

  124.      */

  125.     static byte[] altBase64ToByteArray(String s) {

  126.         return base64ToByteArray(s, true);

  127.     }

  128. 

  129.     private static byte[] base64ToByteArray(String s, boolean alternate) {

  130.         byte[] alphaToInt = (alternate ?  altBase64ToInt : base64ToInt);

  131.         int sLen = s.length();

  132.         int numGroups = sLen4;

  133.         if (4*numGroups != sLen)

  134.             throw new IllegalArgumentException(

  135.                 "String length must be a multiple of four.");

  136.         int missingBytesInLastGroup = 0;

  137.         int numFullGroups = numGroups;

  138.         if (sLen != 0) {

  139.             if (s.charAt(sLen-1) == '=') {

  140.                 missingBytesInLastGroup++;

  141.                 numFullGroups--;

  142.             }

  143.             if (s.charAt(sLen-2) == '=')

  144.                 missingBytesInLastGroup++;

  145.         }

  146.         byte[] result = new byte[3*numGroups - missingBytesInLastGroup];

  147. 

  148.         // Translate all full groups from base64 to byte array elements

  149.         int inCursor = 0, outCursor = 0;

  150.         for (int i=0; i<numFullGroups; i++) {

  151.             int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);

  152.             int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);

  153.             int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);

  154.             int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);

  155.             result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));

  156.             result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));

  157.             result[outCursor++] = (byte) ((ch2 << 6) | ch3);

  158.         }

  159. 

  160.         // Translate partial group, if present

  161.         if (missingBytesInLastGroup != 0) {

  162.             int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);

  163.             int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);

  164.             result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));

  165. 

  166.             if (missingBytesInLastGroup == 1) {

  167.                 int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);

  168.                 result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));

  169.             }

  170.         }

  171.         // assert inCursor == s.length()-missingBytesInLastGroup;

  172.         // assert outCursor == result.length;

  173.         return result;

  174.     }

  175. 

  176.     /**

  177.      * Translates the specified character, which is assumed to be in the

  178.      * "Base 64 Alphabet" into its equivalent 6-bit positive integer.

  179.      *

  180.      * @throw IllegalArgumentException or ArrayOutOfBoundsException if

  181.      *        c is not in the Base64 Alphabet.

  182.      */

  183.     private static int base64toInt(char c, byte[] alphaToInt) {

  184.         int result = alphaToInt[c];

  185.         if (result < 0)

  186.             throw new IllegalArgumentException("Illegal character " + c);

  187.         return result;

  188.     }

  189. 

  190.     /**

  191.      * This array is a lookup table that translates unicode characters

  192.      * drawn from the "Base64 Alphabet" (as specified in Table 1 of RFC 2045)

  193.      * into their 6-bit positive integer equivalents.  Characters that

  194.      * are not in the Base64 alphabet but fall within the bounds of the

  195.      * array are translated to -1.

  196.      */

  197.     private static final byte base64ToInt[] = {

  198.         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  199.         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  200.         -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54,

  201.         55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4,

  202.         5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,

  203.         24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34,

  204.         35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51

  205.     };

  206. 

  207.     /**

  208.      * This array is the analogue of base64ToInt, but for the nonstandard

  209.      * variant that avoids the use of uppercase alphabetic characters.

  210.      */

  211.     private static final byte altBase64ToInt[] = {

  212.         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  213.         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1,

  214.         2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10, 11, -1 , 52, 53, 54, 55, 56, 57,

  215.         58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1,

  216.         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  217.         -1, -1, -1, 17, -1, 18, 19, 21, 20, 26, 27, 28, 29, 30, 31, 32, 33,

  218.         34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50,

  219.         51, 22, 23, 24, 25

  220.     };

  221.     

  222.     public static void main(String args[]) {

  223.         int numRuns  = Integer.parseInt(args[0]);

  224.         int numBytes = Integer.parseInt(args[1]);

  225.         java.util.Random rnd = new java.util.Random();

  226.         for (int i=0; i<numRuns; i++) {

  227.             for (int j=0; j<numBytes; j++) {

  228.                 byte[] arr = new byte[j];

  229.                 for (int k=0; k<j; k++)

  230.                     arr[k] = (byte)rnd.nextInt();

  231. 

  232.                 String s = byteArrayToBase64(arr);

  233.                 byte [] b = base64ToByteArray(s);

  234.                 if (!java.util.Arrays.equals(arr, b))

  235.                     System.out.println("Dismal failure!");

  236. 

  237.                 s = byteArrayToAltBase64(arr);

  238.                 b = altBase64ToByteArray(s);

  239.                 if (!java.util.Arrays.equals(arr, b))

  240.                     System.out.println("Alternate dismal failure!");

  241.             }

  242.         }

  243.     }

  244. }