Base64Encoder.java

package lgpl.haustein;

import java.io.*;

/**
 * Routines to encode and decode using base 64 encoding. 
 * <p>
//kObjects 
//
// Copyright (C) 2001 Stefan Haustein, Oberhausen (Rhld.), Germany
//
// Contributors: 
//
// License: LGPL
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public License
// as published by the Free Software Foundation; either version 2.1 of
// the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
// USA

 * You can now use also javax.mail.internet.MimeUtility
 * and sun.misc.BASE64Encoder.encode.
 * There is a non-public class in Java 1.4+ called java.util.prefs.Base64
 */
public final class Base64Encoder {

    static final char[] charTab = 
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray (); 

    /**
     * @param string
     * @return the input string encoded using Base 64 encoding.
     */
    public static String encode (String string) {
        return encode(string.getBytes()).toString ();
    }
    
    public static String encode (byte [] data) {
        return encode (data, 0, data.length, null).toString ();
    }


    /** Encodes the part of the given byte array denoted by start and
        len to the Base64 format.  The encoded data is appended to the
        given StringBuffer. If no StringBuffer is given, a new one is
        created automatically. The StringBuffer is the return value of
        this method. */
 

    public static StringBuffer encode (byte [] data, int start, int len, StringBuffer buf) {

        if (buf == null) 
            buf = new StringBuffer (data.length * 3 / 2);

        int end = len - 3;
        int i = start;
        int n = 0;

        while (i <= end) {
            int d = (((data [i]) & 0x0ff) << 16) 
                | (((data [i+1]) & 0x0ff) << 8)
                | ((data [i+2]) & 0x0ff);

            buf.append (charTab [(d >> 18) & 63]);
            buf.append (charTab [(d >> 12) & 63]);
            buf.append (charTab [(d >> 6) & 63]);
            buf.append (charTab [d & 63]);

            i += 3;

            if (n++ >= 14) {
                n = 0;
                buf.append ("\r\n");
            }
        }


        if (i == start + len - 2) {
            int d = (((data [i]) & 0x0ff) << 16) 
                | (((data [i+1]) & 255) << 8);

            buf.append (charTab [(d >> 18) & 63]);
            buf.append (charTab [(d >> 12) & 63]);
            buf.append (charTab [(d >> 6) & 63]);
            buf.append ("=");
        }
        else if (i == start + len - 1) {
            int d = ((data [i]) & 0x0ff) << 16;

            buf.append (charTab [(d >> 18) & 63]);
            buf.append (charTab [(d >> 12) & 63]);
            buf.append ("==");
        }

        return buf;
    }


    static int decode (char c) {
        if (c >= 'A' && c <= 'Z') 
            return c - 65;
        else if (c >= 'a' && c <= 'z') 
            return c - 97 + 26;
        else if (c >= '0' && c <= '9')
            return c - 48 + 26 + 26;
        else switch (c) {
        case '+': return 62;
        case '/': return 63;
        case '=': return 0;
        default:
            throw new RuntimeException (new StringBuffer("unexpected code: ").append(c).toString());
        }
    }
                

    /** Decodes the given Base64 encoded String to a new byte array. 
        The byte array holding the decoded data is returned. */


    public static byte [] decode (String s) {    	
        int i = 0;
        ByteArrayOutputStream bos = new ByteArrayOutputStream ();
        int len = s.length ();
        
        while (true) { 
            while (i < len && s.charAt (i) <= ' ') i++;

            if (i == len) break;

            int tri = (decode (s.charAt (i)) << 18)
                + (decode (s.charAt (i+1)) << 12)
                + (decode (s.charAt (i+2)) << 6)
                + (decode (s.charAt (i+3)));
            
            bos.write ((tri >> 16) & 255);
            if (s.charAt (i+2) == '=') break;
            bos.write ((tri >> 8) & 255);
            if (s.charAt (i+3) == '=') break;
            bos.write (tri & 255);

            i += 4;
        }
        return bos.toByteArray ();
    }

  
}