/*
    * %W% %E%
    *
    * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
    * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
    */
   
   package org.asteriskjava.util;
   
  /**
   * Static methods for translating Base64 encoded strings to byte arrays
   * and vice-versa.<p>
   * From java.util.prefs.
   *
   * @author  Josh Bloch
   */
  public class Base64 {
      /**
       * Translates the specified byte array into a Base64 string as per
       * Preferences.put(byte[]).
       */
      public static String byteArrayToBase64(byte[] a) {
          return byteArrayToBase64(a, false);
      }
  
      /**
       * Translates the specified byte array into an "alternate representation"
       * Base64 string.  This non-standard variant uses an alphabet that does
       * not contain the uppercase alphabetic characters, which makes it
       * suitable for use in situations where case-folding occurs.
       */
      public static String byteArrayToAltBase64(byte[] a) {
          return byteArrayToBase64(a, true);
      }
  
      private static String byteArrayToBase64(byte[] a, boolean alternate) {
          int aLen = a.length;
          int numFullGroups = aLen/3;
          int numBytesInPartialGroup = aLen - 3*numFullGroups;
          int resultLen = 4*((aLen + 2)/3);
          StringBuffer result = new StringBuffer(resultLen);
          char[] intToAlpha = (alternate ? intToAltBase64 : intToBase64);
  
          // Translate all full groups from byte array elements to Base64
          int inCursor = 0;
          for (int i=0; i<numFullGroups; i++) {
              int byte0 = a[inCursor++] & 0xff;
              int byte1 = a[inCursor++] & 0xff;
              int byte2 = a[inCursor++] & 0xff;
              result.append(intToAlpha[byte0 >> 2]);
              result.append(intToAlpha[(byte0 << 4)&0x3f | (byte1 >> 4)]);
              result.append(intToAlpha[(byte1 << 2)&0x3f | (byte2 >> 6)]);
              result.append(intToAlpha[byte2 & 0x3f]);
          }
  
          // Translate partial group if present
          if (numBytesInPartialGroup != 0) {
              int byte0 = a[inCursor++] & 0xff;
              result.append(intToAlpha[byte0 >> 2]);
              if (numBytesInPartialGroup == 1) {
                  result.append(intToAlpha[(byte0 << 4) & 0x3f]);
                  result.append("==");
              } else {
                  // assert numBytesInPartialGroup == 2;
                  int byte1 = a[inCursor++] & 0xff;
                  result.append(intToAlpha[(byte0 << 4)&0x3f | (byte1 >> 4)]);
                  result.append(intToAlpha[(byte1 << 2)&0x3f]);
                  result.append('=');
              }
          }
          // assert inCursor == a.length;
          // assert result.length() == resultLen;
          return result.toString();
      }
  
      /**
       * This array is a lookup table that translates 6-bit positive integer
       * index values into their "Base64 Alphabet" equivalents as specified
       * in Table 1 of RFC 2045.
       */
      private static final char intToBase64[] = {
          'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
          'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
          'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
          'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
          '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
      };
  
      /**
       * This array is a lookup table that translates 6-bit positive integer
       * index values into their "Alternate Base64 Alphabet" equivalents.
       * This is NOT the real Base64 Alphabet as per in Table 1 of RFC 2045.
       * This alternate alphabet does not use the capital letters.  It is
       * designed for use in environments where "case folding" occurs.
       */
      private static final char intToAltBase64[] = {
          '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':',
          ';', '<', '>', '@', '[', ']', '^',  '`', '_', '{', '|', '}', '~',
          'a', 'b', 'c', 'd', 'e', 'f', 'g',  'h', 'i', 'j', 'k', 'l', 'm',
         'n', 'o', 'p', 'q', 'r', 's', 't',  'u', 'v', 'w', 'x', 'y', 'z',
         '0', '1', '2', '3', '4', '5', '6',  '7', '8', '9', '+', '?'
     };
 
     /**
      * Translates the specified Base64 string (as per Preferences.get(byte[]))
      * into a byte array.
      *
      * @throw IllegalArgumentException if <tt>s</tt> is not a valid Base64
      *        string.
      */
     public static byte[] base64ToByteArray(String s) {
         return base64ToByteArray(s, false);
     }
 
     /**
      * Translates the specified "alternate representation" Base64 string
      * into a byte array.
      *
      * @throw IllegalArgumentException or ArrayOutOfBoundsException
      *        if <tt>s</tt> is not a valid alternate representation
      *        Base64 string.
      */
     public static byte[] altBase64ToByteArray(String s) {
         return base64ToByteArray(s, true);
     }
 
     private static byte[] base64ToByteArray(String s, boolean alternate) {
         byte[] alphaToInt = (alternate ?  altBase64ToInt : base64ToInt);
         int sLen = s.length();
         int numGroups = sLen/4;
         if (4*numGroups != sLen)
             throw new IllegalArgumentException(
                 "String length must be a multiple of four.");
         int missingBytesInLastGroup = 0;
         int numFullGroups = numGroups;
         if (sLen != 0) {
             if (s.charAt(sLen-1) == '=') {
                 missingBytesInLastGroup++;
                 numFullGroups--;
             }
             if (s.charAt(sLen-2) == '=')
                 missingBytesInLastGroup++;
         }
         byte[] result = new byte[3*numGroups - missingBytesInLastGroup];
 
         // Translate all full groups from base64 to byte array elements
         int inCursor = 0, outCursor = 0;
         for (int i=0; i<numFullGroups; i++) {
             int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
             int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
             int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
             int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);
             result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
             result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
             result[outCursor++] = (byte) ((ch2 << 6) | ch3);
         }
 
         // Translate partial group, if present
         if (missingBytesInLastGroup != 0) {
             int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
             int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
             result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
 
             if (missingBytesInLastGroup == 1) {
                 int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
                 result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
             }
         }
         // assert inCursor == s.length()-missingBytesInLastGroup;
         // assert outCursor == result.length;
         return result;
     }
 
     /**
      * Translates the specified character, which is assumed to be in the
      * "Base 64 Alphabet" into its equivalent 6-bit positive integer.
      *
      * @throw IllegalArgumentException or ArrayOutOfBoundsException if
      *        c is not in the Base64 Alphabet.
      */
     private static int base64toInt(char c, byte[] alphaToInt) {
         int result = alphaToInt[c];
         if (result < 0)
             throw new IllegalArgumentException("Illegal character " + c);
         return result;
     }
 
     /**
      * This array is a lookup table that translates unicode characters
      * drawn from the "Base64 Alphabet" (as specified in Table 1 of RFC 2045)
      * into their 6-bit positive integer equivalents.  Characters that
      * are not in the Base64 alphabet but fall within the bounds of the
      * array are translated to -1.
      */
     private static final byte base64ToInt[] = {
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
         -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54,
         55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4,
         5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
         24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34,
         35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
     };
 
     /**
      * This array is the analogue of base64ToInt, but for the nonstandard
      * variant that avoids the use of uppercase alphabetic characters.
      */
     private static final byte altBase64ToInt[] = {
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1,
         2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10, 11, -1 , 52, 53, 54, 55, 56, 57,
         58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1,
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
         -1, -1, -1, 17, -1, 18, 19, 21, 20, 26, 27, 28, 29, 30, 31, 32, 33,
         34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50,
         51, 22, 23, 24, 25
     };
 }