Base64Coder.java

/*
 * Open Source Physics software is free software as described near the bottom of this code file.
 *
 * For additional information and documentation on Open Source Physics please see:
 * <http://www.opensourcephysics.org/>
 */

/**
* A Base64 Encoder/Decoder.
*
* <p>
* This class is used to encode and decode data in Base64 format as described in RFC 1521.
*
* <p>
* This is "Open Source" software and released under the <a href="http://www.gnu.org/licenses/lgpl.html">GNU/LGPL</a> license.<br>
* It is provided "as is" without warranty of any kind.<br>
* Copyright 2003: Christian d'Heureuse, Inventec Informatik AG, Switzerland.<br>
* Home page: <a href="http://www.source-code.biz">www.source-code.biz</a><br>
*
* <p>
* Version history:<br>
* 2003-07-22 Christian d'Heureuse (chdh): Module created.<br>
* 2005-08-11 chdh: Lincense changed from GPL to LGPL.<br>
* 2006-11-21 chdh:<br>
*  &nbsp; Method encode(String) renamed to encodeString(String).<br>
*  &nbsp; Method decode(String) renamed to decodeString(String).<br>
*  &nbsp; New method encode(byte[],int) added.<br>
*  &nbsp; New method decode(String) added.<br>
* 2007-07-11 Douglas Brown: Deleted methods not needed for OSP.<br>
*/
package org.opensourcephysics.controls;
public class Base64Coder {
  // Mapping table from 6-bit nibbles to Base64 characters.
  private static char[] map1 = new char[64];

  static {
    int i = 0;
    for(char c = 'A'; c<='Z'; c++) {
      map1[i++] = c;
    }
    for(char c = 'a'; c<='z'; c++) {
      map1[i++] = c;
    }
    for(char c = '0'; c<='9'; c++) {
      map1[i++] = c;
    }
    map1[i++] = '+';
    map1[i++] = '/';
  }

  // Mapping table from Base64 characters to 6-bit nibbles.
  private static byte[] map2 = new byte[128];

  static {
    for(int i = 0; i<map2.length; i++) {
      map2[i] = -1;
    }
    for(int i = 0; i<64; i++) {
      map2[map1[i]] = (byte) i;
    }
  }

  /**
   * Encodes a byte array into Base64 format. No blanks or line breaks are
   * inserted.
   *
   * @param in
   *          an array containing the data bytes to be encoded.
   * @return A character array with the Base64 encoded data.
   */
  public static char[] encode(byte[] in) {
    return encode(in, in.length);
  }

  /**
   * Encodes a byte array into Base64 format. No blanks or line breaks are
   * inserted.
   *
   * @param in
   *          an array containing the data bytes to be encoded.
   * @param iLen
   *          number of bytes to process in <code>in</code>.
   * @return A character array with the Base64 encoded data.
   */
  public static char[] encode(byte[] in, int iLen) {
    int oDataLen = (iLen*4+2)/3; // output length without padding
    int oLen = ((iLen+2)/3)*4;   // output length including padding
    char[] out = new char[oLen];
    int ip = 0;
    int op = 0;
    while(ip<iLen) {
      int i0 = in[ip++]&0xff;
      int i1 = (ip<iLen) ? in[ip++]&0xff : 0;
      int i2 = (ip<iLen) ? in[ip++]&0xff : 0;
      int o0 = i0>>>2;
      int o1 = ((i0&3)<<4)|(i1>>>4);
      int o2 = ((i1&0xf)<<2)|(i2>>>6);
      int o3 = i2&0x3F;
      out[op++] = map1[o0];
      out[op++] = map1[o1];
      out[op] = (op<oDataLen) ? map1[o2] : '=';
      op++;
      out[op] = (op<oDataLen) ? map1[o3] : '=';
      op++;
    }
    return out;
  }

  /**
   * Decodes a byte array from Base64 format.
   *
   * @param s
   *          a Base64 String to be decoded.
   * @return An array containing the decoded data bytes.
   * @throws IllegalArgumentException
   *           if the input is not valid Base64 encoded data.
   */
  public static byte[] decode(String s) {
    return decode(s.toCharArray());
  }

  /**
   * Decodes a byte array from Base64 format. No blanks or line breaks are
   * allowed within the Base64 encoded data.
   *
   * @param in
   *          a character array containing the Base64 encoded data.
   * @return An array containing the decoded data bytes.
   * @throws IllegalArgumentException
   *           if the input is not valid Base64 encoded data.
   */
  public static byte[] decode(char[] in) {
    int iLen = in.length;
    if(iLen%4!=0) {
      throw new IllegalArgumentException("Length of Base64 encoded input string is not a multiple of 4."); //$NON-NLS-1$
    }
    while((iLen>0)&&(in[iLen-1]=='=')) {
      iLen--;
    }
    int oLen = (iLen*3)/4;
    byte[] out = new byte[oLen];
    int ip = 0;
    int op = 0;
    while(ip<iLen) {
      int i0 = in[ip++];
      int i1 = in[ip++];
      int i2 = (ip<iLen) ? in[ip++] : 'A';
      int i3 = (ip<iLen) ? in[ip++] : 'A';
      if((i0>127)||(i1>127)||(i2>127)||(i3>127)) {
        throw new IllegalArgumentException("Illegal character in Base64 encoded data."); //$NON-NLS-1$
      }
      int b0 = map2[i0];
      int b1 = map2[i1];
      int b2 = map2[i2];
      int b3 = map2[i3];
      if((b0<0)||(b1<0)||(b2<0)||(b3<0)) {
        throw new IllegalArgumentException("Illegal character in Base64 encoded data."); //$NON-NLS-1$
      }
      int o0 = (b0<<2)|(b1>>>4);
      int o1 = ((b1&0xf)<<4)|(b2>>>2);
      int o2 = ((b2&3)<<6)|b3;
      out[op++] = (byte) o0;
      if(op<oLen) {
        out[op++] = (byte) o1;
      }
      if(op<oLen) {
        out[op++] = (byte) o2;
      }
    }
    return out;
  }

  // Dummy constructor.
  private Base64Coder() {}

} // end class Base64Coder

/*
 * Open Source Physics software is free software; you can redistribute
 * it and/or modify it under the terms of the GNU General Public License (GPL) as
 * published by the Free Software Foundation; either version 2 of the License,
 * or(at your option) any later version.

 * Code that uses any portion of the code in the org.opensourcephysics package
 * or any subpackage (subdirectory) of this package must must also be be released
 * under the GNU GPL license.
 *
 * This software 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston MA 02111-1307 USA
 * or view the license online at http://www.gnu.org/copyleft/gpl.html
 *
 * Copyright (c) 2007  The Open Source Physics project
 *                     http://www.opensourcephysics.org
 */