Base64 encoder/decoder : Base64 « Development Class « Java

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3. Base64

Base64 encoder/decoder

      


/***************************************************************

Copyright (c) 1998, 1999 Nate Sammons <nate@protomatter.com>  
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 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
Library General Public License for more details.

You should have received a copy of the GNU Library 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.

Contact support@protomatter.com with your questions, comments,
gripes, praise, etc...

***************************************************************/


/***************************************************************
  - moved to the net.matuschek.util tree by Daniel Matuschek
  - replaced deprecated getBytes() method in method decode
  - added String encode(String) method to encode a String to 
    base64
 ***************************************************************/

/**
 * Base64 encoder/decoder.  Does not stream, so be careful with
 * using large amounts of data
 *
 * @author Nate Sammons
 * @author Daniel Matuschek
 * @version $Id: Base64.java,v 1.4 2001/04/17 10:09:27 matuschd Exp $
 */
public class Base64
{

  private Base64()
  {
    super();
  }

  /**
   *  Encode some data and return a String.
   */
  public final static String encode(byte[] d)
  {
    if (d == null) return null;
    byte data[] = new byte[d.length+2];
    System.arraycopy(d, 0, data, 0, d.length);
    byte dest[] = new byte[(data.length/3)*4];

    // 3-byte to 4-byte conversion
    for (int sidx = 0, didx=0; sidx < d.length; sidx += 3, didx += 4)
    {
      dest[didx]   = (byte) ((data[sidx] >>> 2) & 077);
      dest[didx+1] = (byte) ((data[sidx+1] >>> 4) & 017 |
                  (data[sidx] << 4) & 077);
      dest[didx+2] = (byte) ((data[sidx+2] >>> 6) & 003 |
                  (data[sidx+1] << 2) & 077);
      dest[didx+3] = (byte) (data[sidx+2] & 077);
    }

    // 0-63 to ascii printable conversion
    for (int idx = 0; idx <dest.length; idx++)
    {
      if (dest[idx] < 26)     dest[idx] = (byte)(dest[idx] + 'A');
      else if (dest[idx] < 52)  dest[idx] = (byte)(dest[idx] + 'a' - 26);
      else if (dest[idx] < 62)  dest[idx] = (byte)(dest[idx] + '0' - 52);
      else if (dest[idx] < 63)  dest[idx] = (byte)'+';
      else            dest[idx] = (byte)'/';
    }

    // add padding
    for (int idx = dest.length-1; idx > (d.length*4)/3; idx--)
    {
      dest[idx] = (byte)'=';
    }
    return new String(dest);
  }

  /**
   * Encode a String using Base64 using the default platform encoding
   **/
  public final static String encode(String s) {
    return encode(s.getBytes());
  }

  /**
   *  Decode data and return bytes.
   */
  public final static byte[] decode(String str)
  {
    if (str == null)  return  null;
    byte data[] = str.getBytes();
    return decode(data);
  }

  /**
   *  Decode data and return bytes.  Assumes that the data passed
   *  in is ASCII text.
   */
  public final static byte[] decode(byte[] data)
  {
    int tail = data.length;
    while (data[tail-1] == '=')  tail--;
    byte dest[] = new byte[tail - data.length/4];

    // ascii printable to 0-63 conversion
    for (int idx = 0; idx <data.length; idx++)
    {
      if (data[idx] == '=')    data[idx] = 0;
      else if (data[idx] == '/') data[idx] = 63;
      else if (data[idx] == '+') data[idx] = 62;
      else if (data[idx] >= '0'  &&  data[idx] <= '9')
        data[idx] = (byte)(data[idx] - ('0' - 52));
      else if (data[idx] >= 'a'  &&  data[idx] <= 'z')
        data[idx] = (byte)(data[idx] - ('a' - 26));
      else if (data[idx] >= 'A'  &&  data[idx] <= 'Z')
        data[idx] = (byte)(data[idx] - 'A');
    }

    // 4-byte to 3-byte conversion
    int sidx, didx;
    for (sidx = 0, didx=0; didx < dest.length-2; sidx += 4, didx += 3)
    {
      dest[didx]   = (byte) ( ((data[sidx] << 2) & 255) |
              ((data[sidx+1] >>> 4) & 3) );
      dest[didx+1] = (byte) ( ((data[sidx+1] << 4) & 255) |
              ((data[sidx+2] >>> 2) & 017) );
      dest[didx+2] = (byte) ( ((data[sidx+2] << 6) & 255) |
              (data[sidx+3] & 077) );
    }
    if (didx < dest.length)
    {
      dest[didx]   = (byte) ( ((data[sidx] << 2) & 255) |
              ((data[sidx+1] >>> 4) & 3) );
    }
    if (++didx < dest.length)
    {
      dest[didx]   = (byte) ( ((data[sidx+1] << 4) & 255) |
              ((data[sidx+2] >>> 2) & 017) );
    }
    return dest;
  }

  /**
   *  A simple test that encodes and decodes the first commandline argument.
   */
  public static final void main(String[] args)
  {
    if (args.length != 1)
    {
      System.out.println("Usage: Base64 string");
      System.exit(0);
    }
    try
    {
      String e = Base64.encode(args[0].getBytes());
      String d = new String(Base64.decode(e));
      System.out.println("Input   = '" + args[0] + "'");
      System.out.println("Encoded = '" + e + "'");
      System.out.println("Decoded = '" + d + "'");
    }
    catch (Exception x)
    {
      x.printStackTrace();
    }
  }
}

   
    
    
    
    
    
  

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