Base64.java

package org.threadly.litesockets.utils;
/*
 * Base64.java
 *
 * Brazil project web application toolkit,
 * export version: 2.0 
 * Copyright (c) 2000-2002 Sun Microsystems, Inc.
 *
 * Sun Public License Notice
 *
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is included as
 * the file "license.terms", and also available at
 * http://www.sun.com/
 * 
 * The Original Code is from:
 *    Brazil project web application toolkit release 2.0.
 * The Initial Developer of the Original Code is: cstevens.
 * Portions created by cstevens are Copyright (C) Sun Microsystems,
 * Inc. All Rights Reserved.
 * 
 * Contributor(s): cstevens, suhler.
 *
 * Version:  1.9
 * Created by cstevens on 00/04/17
 * Last modified by suhler on 02/07/24 10:49:48
 */

/**
 * Utility to base64 encode and decode a string.
 * @author      Stephen Uhler
 * @version 1.9, 02/07/24
 */
public class Base64 {
  private static final String CHARSET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

  private Base64() {}

  /**
   * base-64 encode a string.
   * @param str   The ascii string to encode.
   * @return   The base64 encoded result.
   */
  public static String encode(final String str) {
    return encode(str.getBytes());
  }

  /**
   * base-64 encode a byte array.
   * @param src The byte array to encode.
   * @return   The base64 encoded result.
   */
  public static String encode(final byte[] src) {
    return encode(src, 0, src.length);
  }

  /**
   * base-64 encode a byte array.
   * @param src The byte array to encode.
   * @param start The starting index.
   * @param length The number of bytes.
   * @return   The base64 encoded result.
   */
  public static String encode(final byte[] src, final int start, final int length) {
    StringBuilder sb = new StringBuilder();
    int x = 0;
    int state = 0;  // which char in pattern
    int old = 0;  // previous byte
    int max = length + start;
    for (int srcIndex = start; srcIndex<max; srcIndex++) {
      x = src[srcIndex];
      switch (++state) {
        case 1:
          sb.append(CHARSET.charAt((x>>2) & 0x3f));
          break;
        case 2:
          sb.append(CHARSET.charAt(((old<<4)&0x30) | ((x>>4)&0xf)));
          break;
        case 3:
          sb.append(CHARSET.charAt(((old<<2)&0x3C) | ((x>>6)&0x3)));
          sb.append(CHARSET.charAt(x&0x3F));
          state = 0;
          break;
        default:
          break;
      }
      old = x;
    }

    // now clean up the end bytes
    if(state == 1) {
      sb.append(CHARSET.charAt((old<<4) & 0x30)).append("==");
    } else if(state == 2) {
      sb.append(CHARSET.charAt((old<<2) & 0x3c)).append("=");
    }
    
    return sb.toString();
  }

  /**
   * A Base64 decoder.  This implementation is slow, and 
   * doesn't handle wrapped lines.
   * The output is undefined if there are errors in the input.
   * @param s   a Base64 encoded string.
   * @return   The byte array eith the decoded result.
   */
  public static byte[] decode(final String s) {
    int end = 0;  // end state
    if (s.endsWith("=")) {
      end++;
    }
    if (s.endsWith("==")) {
      end++;
    }
    int len = (s.length() + 3)/4 * 3 - end;
    byte[] result = new byte[len];
    int dst = 0;
    try {
      for(int src = 0; src< s.length(); src++) {
        int code =  CHARSET.indexOf(s.charAt(src));
        if (code == -1) {
          break;
        }
        switch (src%4) {
          case 0:
            result[dst] = (byte) (code<<2);
            break;
          case 1: 
            result[dst++] |= (byte) ((code>>4) & 0x3);
            result[dst] = (byte) (code<<4);
            break;
          case 2:
            result[dst++] |= (byte) ((code>>2) & 0xf);
            result[dst] = (byte) (code<<6);
            break;
          case 3:
            result[dst++] |= (byte) (code & 0x3f);
            break;
          default:
            break;
        }
      }
    } catch (ArrayIndexOutOfBoundsException e) {}
    return result;
  }
}