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QuartzDesk Public API library required for QuartzDesk Standard and Enterprise edition installations. This library must be placed on the classpath of the Quartz scheduler based application that is managed by QuartzDesk. It is important that this library is loaded by the same classloader that loads the Quartz scheduler API used by the application.

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/*
 * Copyright (c) 2013-2019 QuartzDesk.com. All Rights Reserved.
 * QuartzDesk.com PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package com.quartzdesk.api.common.encoding;

import com.quartzdesk.api.ApiConst;

import java.io.ByteArrayOutputStream;
import java.io.UnsupportedEncodingException;

/**
 * This is a utility class which is used to decode a string in the MIME
 * BASE64 format into a byte array. For further information about the MIME
 * BASE64 encoding, see RFC2045.
 *
 * @version $Id:$
 */
public final class BASE64Decoder
{
  /**
   * Private constructor of a utility class.
   */
  private BASE64Decoder()
  {
  }


  /**
   * Decodes a string in the MIME BASE64 format into a byte array.
   *
   * @param s the string in the MIME BASE64 format.
   * @return the byte array of decoded data.
   * @throws EncodingException when the string s is not in MIME BASE64 format.
   */
  public static byte[] decode( String s )
      throws EncodingException
  {
    // CSOFF: MagicNumber
    if ( s == null )
      return null;

    int first;
    int second;
    int third;
    int fourth;

    try
    {
      ByteArrayOutputStream ba = new ByteArrayOutputStream( s.length() );

      byte[] bytes = s.getBytes( ApiConst.ENCODING_ISO_8859_1 );

      for ( int i = 0; i < bytes.length; )
      {
        // skip empty lines
        if ( bytes[i] == '\n' || bytes[i] == '\r' )
        {
          i++;
          continue;
        }

        first = translate( bytes[i++] );
        second = translate( bytes[i++] );
        third = translate( bytes[i++] );
        fourth = translate( bytes[i++] );

        if ( first != -1 )
        {
          if ( second != -1 )
          {
            // append the first decoded char
            ba.write( (byte) ( ( first << 2 ) | ( ( second & 0x30 ) >>> 4 ) ) );
            if ( third != -1 )
            {
              // append the second decoded char
              ba.write( (byte) ( ( ( second & 0xf ) << 4 ) | ( ( third & 0x3c ) >>> 2 ) ) );
              if ( fourth != -1 )
              {
                // append the third decoded character
                ba.write( (byte) ( ( ( third & 0x03 ) << 6 ) | fourth ) );
              }
              else
              {
                // the fourth character is the padding
                break;
              }
            }
            else
            {
              // the third character is the padding and the fourth should be too
              if ( fourth != -1 )
                throw new EncodingException( "Not MIME BASE64 data format." );
              break;
            }
          }
          else
          {
            // second character in a quad is the padding character
            throw new EncodingException( "Second character in a quad cannot be =." );
          }
        }
        else
        {
          // first character in a quad is the padding character
          throw new EncodingException( "First character in a quad cannot be =." );
        }
      }
      return ba.toByteArray();
    }
    catch ( UnsupportedEncodingException e )
    {
      throw new EncodingException( "Unable to extract input string bytes.", e );
    }
    // CSON: MagicNumber
  }


  /**
   * Returns the position of byte b in the MIME BASE64 alphabet. Values
   * from the range <0,63> are returned. Value of -1 is returned when
   * b is the padding character '='.
   *
   * @param b a byte to translate.
   * @return the position of the specified byte in the MIME BASE64 alphabet.
   * @throws EncodingException if byte b is not from the MIME BASE64 alphabet.
   */
  private static int translate( byte b )
      throws EncodingException
  {
    // CSOFF: MagicNumber
    if ( b >= 'A' && b <= 'Z' ) return b - 'A';
    if ( b >= 'a' && b <= 'z' ) return b - 'a' + 26;
    if ( b >= '0' && b <= '9' ) return b - '0' + 52;
    if ( b == '+' ) return 62;
    if ( b == '/' ) return 63;
    if ( b == '=' ) return -1;
    throw new EncodingException( "Not MIME BASE64 character: 0x" + Character.digit( (char) b, 16 ) );
    // CSON: MagicNumber
  }
}