/* Base64Converter.java

   David W. Croft, 08/06/1998
   Java Tip 47, www.JavaWorld.com, April 6th 2000
   http://www.javaworld.com/javaworld/javatips/jw-javatip47.html

   "username:password" is passed in via encode(),
   which returns the a BASE 64 encoded authorization string.
   For details on BASE 64 see RFC 1421.
*/


  public class Base64Converter
  {

    public static final char [ ] alphabet = {
      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', // 0 to 7
      'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 8 to 15
      'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 16 to 23
      'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', // 24 to 31
      'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', // 32 to 39
      'o', 'p', 'q', 'r', 's', 't', 'u', 'v', // 40 to 47
      'w', 'x', 'y', 'z', '0', '1', '2', '3', // 48 to 55
      '4', '5', '6', '7', '8', '9', '+', '/' }; // 56 to 63

    public static String encode ( String s )
    {
      return encode ( s.getBytes ( ) );
    }

    public static String encode ( byte [ ] octetString )
    {
      int bits24;
      int bits6;
      char [ ] out = new char [ ( ( octetString.length - 1 ) / 3 + 1 ) * 4 ];

      int outIndex = 0;
      int i = 0;

      while ( ( i + 3 ) <= octetString.length )
        {
          // store the octets
          bits24 = ( octetString [ i++ ] & 0xFF ) << 16; 
          bits24 |= ( octetString [ i++ ] & 0xFF ) << 8; 
          bits24 |= ( octetString [ i++ ] & 0xFF ) << 0;
		  bits6 = ( bits24 & 0x00FC0000 ) >> 18; 
          out [ outIndex++ ] = alphabet [ bits6 ];
          bits6 = ( bits24 & 0x0003F000 ) >> 12; 
          out [ outIndex++ ] = alphabet [ bits6 ];
          bits6 = ( bits24 & 0x00000FC0 ) >> 6; 
          out [ outIndex++ ] = alphabet [ bits6 ];
          bits6 = ( bits24 & 0x0000003F );
          out [ outIndex++ ] = alphabet [ bits6 ]; 
        }

      if ( octetString.length - i == 2 )
        {
          // store the octets 
          bits24 = ( octetString [ i ] & 0xFF ) << 16; 
          bits24 |= ( octetString [ i + 1 ] & 0xFF ) << 8;

          bits6 = ( bits24 & 0x00FC0000 ) >> 18;
          out [ outIndex++ ] = alphabet [ bits6 ]; 
          bits6 = ( bits24 & 0x0003F000 ) >> 12; 
          out [ outIndex++ ] = alphabet [ bits6 ]; 
          bits6 = ( bits24 & 0x00000FC0 ) >> 6; 
          out [ outIndex++ ] = alphabet [ bits6 ];
		  // padding
          out [ outIndex++ ] = '='; 
        }
        else if ( octetString.length - i == 1 )
        {
          // store the octets 
          bits24 = ( octetString [ i ] & 0xFF ) << 16;

          bits6 = ( bits24 & 0x00FC0000 ) >> 18;
          out [ outIndex++ ] = alphabet [ bits6 ];
          bits6 = ( bits24 & 0x0003F000 ) >> 12; 
          out [ outIndex++ ] = alphabet [ bits6 ];

          // padding
          out [ outIndex++ ] = '='; 
        }

    return new String ( out );
  }

}