/*
 * reserved comment block
 * DO NOT REMOVE OR ALTER!
 */
/*
 * Copyright  1999-2004 The Apache Software Foundation.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package com.sun.org.apache.xml.internal.security.utils;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.math.BigInteger;

import com.sun.org.apache.xml.internal.security.exceptions.Base64DecodingException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.Text;


/**
 * Implementation of MIME's Base64 encoding and decoding conversions.
 * Optimized code. (raw version taken from oreilly.jonathan.util,
 * and currently com.sun.org.apache.xerces.internal.ds.util.Base64)
 *
 * @author Raul Benito(Of the xerces copy, and little adaptations).
 * @author Anli Shundi
 * @author Christian Geuer-Pollmann
 * @see <A HREF="ftp://ftp.isi.edu/in-notes/rfc2045.txt">RFC 2045</A>
 * @see com.sun.org.apache.xml.internal.security.transforms.implementations.TransformBase64Decode
 */
public class Base64 {


   /** Field BASE64DEFAULTLENGTH */
   public static final int BASE64DEFAULTLENGTH = 76;

   private Base64() {
     // we don't allow instantiation
   }

   /**
    * Returns a byte-array representation of a <code>{@link BigInteger}<code>.
    * No sign-bit is outputed.
    *
    * <b>N.B.:</B> <code>{@link BigInteger}<code>'s toByteArray
    * retunrs eventually longer arrays because of the leading sign-bit.
    *
    * @param big <code>BigInteger<code> to be converted
    * @param bitlen <code>int<code> the desired length in bits of the representation
    * @return a byte array with <code>bitlen</code> bits of <code>big</code>
    */
   static final byte[] getBytes(BigInteger big, int bitlen) {

      //round bitlen
      bitlen = ((bitlen + 7) >> 3) << 3;

      if (bitlen < big.bitLength()) {
         throw new IllegalArgumentException(I18n
            .translate("utils.Base64.IllegalBitlength"));
      }

      byte[] bigBytes = big.toByteArray();

      if (((big.bitLength() % 8) != 0)
              && (((big.bitLength() / 8) + 1) == (bitlen / 8))) {
         return bigBytes;
      }

         // some copying needed
         int startSrc = 0;    // no need to skip anything
         int bigLen = bigBytes.length;    //valid length of the string

         if ((big.bitLength() % 8) == 0) {    // correct values
            startSrc = 1;    // skip sign bit

            bigLen--;    // valid length of the string
         }

         int startDst = bitlen / 8 - bigLen;    //pad with leading nulls
         byte[] resizedBytes = new byte[bitlen / 8];

         System.arraycopy(bigBytes, startSrc, resizedBytes, startDst, bigLen);

         return resizedBytes;

   }

   /**
    * Encode in Base64 the given <code>{@link BigInteger}<code>.
    *
    * @param big
    * @return String with Base64 encoding
    */
   public static final String encode(BigInteger big) {
      return encode(getBytes(big, big.bitLength()));
   }

   /**
    * Returns a byte-array representation of a <code>{@link BigInteger}<code>.
    * No sign-bit is outputed.
    *
    * <b>N.B.:</B> <code>{@link BigInteger}<code>'s toByteArray
    * retunrs eventually longer arrays because of the leading sign-bit.
    *
    * @param big <code>BigInteger<code> to be converted
    * @param bitlen <code>int<code> the desired length in bits of the representation
    * @return a byte array with <code>bitlen</code> bits of <code>big</code>
    */
   public static final  byte[] encode(BigInteger big, int bitlen) {

      //round bitlen
      bitlen = ((bitlen + 7) >> 3) << 3;

      if (bitlen < big.bitLength()) {
         throw new IllegalArgumentException(I18n
            .translate("utils.Base64.IllegalBitlength"));
      }

      byte[] bigBytes = big.toByteArray();

      if (((big.bitLength() % 8) != 0)
              && (((big.bitLength() / 8) + 1) == (bitlen / 8))) {
         return bigBytes;
      }

         // some copying needed
         int startSrc = 0;    // no need to skip anything
         int bigLen = bigBytes.length;    //valid length of the string

         if ((big.bitLength() % 8) == 0) {    // correct values
            startSrc = 1;    // skip sign bit

            bigLen--;    // valid length of the string
         }

         int startDst = bitlen / 8 - bigLen;    //pad with leading nulls
         byte[] resizedBytes = new byte[bitlen / 8];

         System.arraycopy(bigBytes, startSrc, resizedBytes, startDst, bigLen);

         return resizedBytes;

   }

   /**
    * Method decodeBigIntegerFromElement
    *
    * @param element
    * @return the biginter obtained from the node
    * @throws Base64DecodingException
    */
   public static final BigInteger decodeBigIntegerFromElement(Element element) throws Base64DecodingException
   {
      return new BigInteger(1, Base64.decode(element));
   }

   /**
    * Method decodeBigIntegerFromText
    *
    * @param text
    * @return the biginter obtained from the text node
    * @throws Base64DecodingException
    */
   public static final BigInteger decodeBigIntegerFromText(Text text) throws Base64DecodingException
   {
      return new BigInteger(1, Base64.decode(text.getData()));
   }

   /**
    * This method takes an (empty) Element and a BigInteger and adds the
    * base64 encoded BigInteger to the Element.
    *
    * @param element
    * @param biginteger
    */
   public static final void fillElementWithBigInteger(Element element,
           BigInteger biginteger) {

      String encodedInt = encode(biginteger);

      if (encodedInt.length() > 76) {
         encodedInt = "\n" + encodedInt + "\n";
      }

      Document doc = element.getOwnerDocument();
      Text text = doc.createTextNode(encodedInt);

      element.appendChild(text);
   }

   /**
    * Method decode
    *
    * Takes the <CODE>Text</CODE> children of the Element and interprets
    * them as input for the <CODE>Base64.decode()</CODE> function.
    *
    * @param element
    * @return the byte obtained of the decoding the element
    * $todo$ not tested yet
    * @throws Base64DecodingException
    */
   public static final byte[] decode(Element element) throws Base64DecodingException {

      Node sibling = element.getFirstChild();
      StringBuffer sb = new StringBuffer();

      while (sibling!=null) {
         if (sibling.getNodeType() == Node.TEXT_NODE) {
            Text t = (Text) sibling;

            sb.append(t.getData());
         }
         sibling=sibling.getNextSibling();
      }

      return decode(sb.toString());
   }

   /**
    * Method encodeToElement
    *
    * @param doc
    * @param localName
    * @param bytes
    * @return an Element with the base64 encoded in the text.
    *
    */
   public static final Element encodeToElement(Document doc, String localName,
                                         byte[] bytes) {

      Element el = XMLUtils.createElementInSignatureSpace(doc, localName);
      Text text = doc.createTextNode(encode(bytes));

      el.appendChild(text);

      return el;
   }

   /**
    * Method decode
    *
    *
    * @param base64
    * @return the UTF bytes of the base64
    * @throws Base64DecodingException
    *
    */
   public final static byte[] decode(byte[] base64) throws Base64DecodingException  {
         return decodeInternal(base64, -1);
   }



   /**
    * Encode a byte array and fold lines at the standard 76th character unless
    * ignore line breaks property is set.
    *
    * @param binaryData <code>byte[]<code> to be base64 encoded
    * @return the <code>String<code> with encoded data
    */
   public static final String encode(byte[] binaryData) {
      return XMLUtils.ignoreLineBreaks()
         ? encode(binaryData, Integer.MAX_VALUE)
         : encode(binaryData, BASE64DEFAULTLENGTH);
   }

   /**
    * Base64 decode the lines from the reader and return an InputStream
    * with the bytes.
    *
    *
    * @param reader
    * @return InputStream with the decoded bytes
    * @exception IOException passes what the reader throws
    * @throws IOException
    * @throws Base64DecodingException
    */
   public final static byte[] decode(BufferedReader reader)
           throws IOException, Base64DecodingException {

      UnsyncByteArrayOutputStream baos = new UnsyncByteArrayOutputStream();
      String line;

      while (null != (line = reader.readLine())) {
         byte[] bytes = decode(line);

         baos.write(bytes);
      }

      return baos.toByteArray();
   }

   static private final int  BASELENGTH         = 255;
   static private final int  LOOKUPLENGTH       = 64;
   static private final int  TWENTYFOURBITGROUP = 24;
   static private final int  EIGHTBIT           = 8;
   static private final int  SIXTEENBIT         = 16;
   static private final int  FOURBYTE           = 4;
   static private final int  SIGN               = -128;
   static private final char PAD                = '=';
   static final private byte [] base64Alphabet        = new byte[BASELENGTH];
   static final private char [] lookUpBase64Alphabet  = new char[LOOKUPLENGTH];

   static {

       for (int i = 0; i<BASELENGTH; i++) {
           base64Alphabet[i] = -1;
       }
       for (int i = 'Z'; i >= 'A'; i--) {
           base64Alphabet[i] = (byte) (i-'A');
       }
       for (int i = 'z'; i>= 'a'; i--) {
           base64Alphabet[i] = (byte) ( i-'a' + 26);
       }

       for (int i = '9'; i >= '0'; i--) {
           base64Alphabet[i] = (byte) (i-'0' + 52);
       }

       base64Alphabet['+']  = 62;
       base64Alphabet['/']  = 63;

       for (int i = 0; i<=25; i++)
           lookUpBase64Alphabet[i] = (char)('A'+i);

       for (int i = 26,  j = 0; i<=51; i++, j++)
           lookUpBase64Alphabet[i] = (char)('a'+ j);

       for (int i = 52,  j = 0; i<=61; i++, j++)
           lookUpBase64Alphabet[i] = (char)('0' + j);
       lookUpBase64Alphabet[62] = '+';
       lookUpBase64Alphabet[63] = '/';

   }

   protected static final boolean isWhiteSpace(byte octect) {
       return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);
   }

   protected static final boolean isPad(byte octect) {
       return (octect == PAD);
   }


   /**
    * Encodes hex octects into Base64
    *
    * @param binaryData Array containing binaryData
    * @return Encoded Base64 array
    */
   /**
    * Encode a byte array in Base64 format and return an optionally
    * wrapped line.
    *
    * @param binaryData <code>byte[]</code> data to be encoded
    * @param length <code>int<code> length of wrapped lines; No wrapping if less than 4.
    * @return a <code>String</code> with encoded data
    */
    public static final String  encode(byte[] binaryData,int length) {

        if (length<4) {
                length=Integer.MAX_VALUE;
        }

       if (binaryData == null)
           return null;

       int      lengthDataBits    = binaryData.length*EIGHTBIT;
       if (lengthDataBits == 0) {
           return "";
       }

       int      fewerThan24bits   = lengthDataBits%TWENTYFOURBITGROUP;
       int      numberTriplets    = lengthDataBits/TWENTYFOURBITGROUP;
       int      numberQuartet     = fewerThan24bits != 0 ? numberTriplets+1 : numberTriplets;
       int      quartesPerLine    = length/4;
       int      numberLines       = (numberQuartet-1)/quartesPerLine;
       char     encodedData[]     = null;

       encodedData = new char[numberQuartet*4+numberLines];

       byte k=0, l=0, b1=0,b2=0,b3=0;

       int encodedIndex = 0;
       int dataIndex   = 0;
       int i           = 0;


       for (int line = 0; line < numberLines; line++) {
           for (int quartet = 0; quartet < 19; quartet++) {
               b1 = binaryData[dataIndex++];
               b2 = binaryData[dataIndex++];
               b3 = binaryData[dataIndex++];


               l  = (byte)(b2 & 0x0f);
               k  = (byte)(b1 & 0x03);

               byte val1 = ((b1 & SIGN)==0)?(byte)(b1>>2):(byte)((b1)>>2^0xc0);

               byte val2 = ((b2 & SIGN)==0)?(byte)(b2>>4):(byte)((b2)>>4^0xf0);
               byte val3 = ((b3 & SIGN)==0)?(byte)(b3>>6):(byte)((b3)>>6^0xfc);


               encodedData[encodedIndex++] = lookUpBase64Alphabet[ val1 ];
               encodedData[encodedIndex++] = lookUpBase64Alphabet[ val2 | ( k<<4 )];
               encodedData[encodedIndex++] = lookUpBase64Alphabet[ (l <<2 ) | val3 ];
               encodedData[encodedIndex++] = lookUpBase64Alphabet[ b3 & 0x3f ];

               i++;
           }
                encodedData[encodedIndex++] = 0xa;
       }

       for (; i<numberTriplets; i++) {
           b1 = binaryData[dataIndex++];
           b2 = binaryData[dataIndex++];
           b3 = binaryData[dataIndex++];


           l  = (byte)(b2 & 0x0f);
           k  = (byte)(b1 & 0x03);

           byte val1 = ((b1 & SIGN)==0)?(byte)(b1>>2):(byte)((b1)>>2^0xc0);

           byte val2 = ((b2 & SIGN)==0)?(byte)(b2>>4):(byte)((b2)>>4^0xf0);
           byte val3 = ((b3 & SIGN)==0)?(byte)(b3>>6):(byte)((b3)>>6^0xfc);


           encodedData[encodedIndex++] = lookUpBase64Alphabet[ val1 ];
           encodedData[encodedIndex++] = lookUpBase64Alphabet[ val2 | ( k<<4 )];
           encodedData[encodedIndex++] = lookUpBase64Alphabet[ (l <<2 ) | val3 ];
           encodedData[encodedIndex++] = lookUpBase64Alphabet[ b3 & 0x3f ];
       }

       // form integral number of 6-bit groups
       if (fewerThan24bits == EIGHTBIT) {
           b1 = binaryData[dataIndex];
           k = (byte) ( b1 &0x03 );
          byte val1 = ((b1 & SIGN)==0)?(byte)(b1>>2):(byte)((b1)>>2^0xc0);
           encodedData[encodedIndex++] = lookUpBase64Alphabet[ val1 ];
           encodedData[encodedIndex++] = lookUpBase64Alphabet[ k<<4 ];
           encodedData[encodedIndex++] = PAD;
           encodedData[encodedIndex++] = PAD;
       } else if (fewerThan24bits == SIXTEENBIT) {
           b1 = binaryData[dataIndex];
           b2 = binaryData[dataIndex +1 ];
           l = ( byte ) ( b2 &0x0f );
           k = ( byte ) ( b1 &0x03 );

           byte val1 = ((b1 & SIGN)==0)?(byte)(b1>>2):(byte)((b1)>>2^0xc0);
           byte val2 = ((b2 & SIGN)==0)?(byte)(b2>>4):(byte)((b2)>>4^0xf0);

           encodedData[encodedIndex++] = lookUpBase64Alphabet[ val1 ];
           encodedData[encodedIndex++] = lookUpBase64Alphabet[ val2 | ( k<<4 )];
           encodedData[encodedIndex++] = lookUpBase64Alphabet[ l<<2 ];
           encodedData[encodedIndex++] = PAD;
       }

       //encodedData[encodedIndex] = 0xa;

       return new String(encodedData);
   }

    /**
     * Decodes Base64 data into octects
     *
     * @param encoded String containing base64 encoded data
     * @return byte array containing the decoded data
     * @throws Base64DecodingException if there is a problem decoding the data
     */
    public final static byte[] decode(String encoded) throws Base64DecodingException {

        if (encoded == null)
                return null;
        byte []bytes=new byte[encoded.length()];
        int len=getBytesInternal(encoded, bytes);
        return decodeInternal(bytes, len);
        }

    protected static final int getBytesInternal(String s,byte[] result) {
        int length=s.length();

        int newSize=0;
        for (int i = 0; i < length; i++) {
            byte dataS=(byte)s.charAt(i);
            if (!isWhiteSpace(dataS))
                result[newSize++] = dataS;
        }
        return newSize;

    }
   protected final static byte[] decodeInternal(byte[] base64Data, int len) throws Base64DecodingException {
       // remove white spaces
           if (len==-1)
          len = removeWhiteSpace(base64Data);

       if (len%FOURBYTE != 0) {
           throw new Base64DecodingException("decoding.divisible.four");
           //should be divisible by four
       }

       int      numberQuadruple    = (len/FOURBYTE );

       if (numberQuadruple == 0)
           return new byte[0];

       byte     decodedData[]      = null;
       byte     b1=0,b2=0,b3=0, b4=0;


       int i = 0;
       int encodedIndex = 0;
       int dataIndex    = 0;

       //decodedData      = new byte[ (numberQuadruple)*3];
       dataIndex=(numberQuadruple-1)*4;
       encodedIndex=(numberQuadruple-1)*3;
       //first last bits.
       b1 = base64Alphabet[base64Data[dataIndex++]];
       b2 = base64Alphabet[base64Data[dataIndex++]];
       if ((b1==-1) || (b2==-1)) {
                throw new Base64DecodingException("decoding.general");//if found "no data" just return null
        }


        byte d3,d4;
        b3 = base64Alphabet[d3=base64Data[dataIndex++]];
        b4 = base64Alphabet[d4=base64Data[dataIndex++]];
        if ((b3==-1 ) || (b4==-1) ) {
                //Check if they are PAD characters
            if (isPad( d3 ) && isPad( d4)) {               //Two PAD e.g. 3c[Pad][Pad]
                if ((b2 & 0xf) != 0)//last 4 bits should be zero
                        throw new Base64DecodingException("decoding.general");
                decodedData = new byte[ encodedIndex + 1 ];
                decodedData[encodedIndex]   = (byte)(  b1 <<2 | b2>>4 ) ;
            } else if (!isPad( d3) && isPad(d4)) {               //One PAD  e.g. 3cQ[Pad]
                if ((b3 & 0x3 ) != 0)//last 2 bits should be zero
                        throw new Base64DecodingException("decoding.general");
                decodedData = new byte[ encodedIndex + 2 ];
                decodedData[encodedIndex++] = (byte)(  b1 <<2 | b2>>4 );
                decodedData[encodedIndex]   = (byte)(((b2 & 0xf)<<4 ) |( (b3>>2) & 0xf) );
            } else {
                throw new Base64DecodingException("decoding.general");//an error  like "3c[Pad]r", "3cdX", "3cXd", "3cXX" where X is non data
            }
        } else {
            //No PAD e.g 3cQl
            decodedData = new byte[encodedIndex+3];
            decodedData[encodedIndex++] = (byte)(  b1 <<2 | b2>>4 ) ;
            decodedData[encodedIndex++] = (byte)(((b2 & 0xf)<<4 ) |( (b3>>2) & 0xf) );
            decodedData[encodedIndex++] = (byte)( b3<<6 | b4 );
        }
        encodedIndex=0;
        dataIndex=0;
       //the begin
       for (i=numberQuadruple-1; i>0; i--) {
           b1 = base64Alphabet[base64Data[dataIndex++]];
           b2 = base64Alphabet[base64Data[dataIndex++]];
           b3 = base64Alphabet[base64Data[dataIndex++]];
           b4 = base64Alphabet[base64Data[dataIndex++]];

           if ( (b1==-1) ||
                        (b2==-1) ||
                        (b3==-1) ||
                        (b4==-1) ) {
                   throw new Base64DecodingException("decoding.general");//if found "no data" just return null
           }

           decodedData[encodedIndex++] = (byte)(  b1 <<2 | b2>>4 ) ;
           decodedData[encodedIndex++] = (byte)(((b2 & 0xf)<<4 ) |( (b3>>2) & 0xf) );
           decodedData[encodedIndex++] = (byte)( b3<<6 | b4 );
       }
       return decodedData;
   }
   /**
    * Decodes Base64 data into  outputstream
    *
    * @param base64Data String containing Base64 data
    * @param os the outputstream
    * @throws IOException
    * @throws Base64DecodingException
    */
   public final static void decode(String base64Data,
        OutputStream os) throws Base64DecodingException, IOException {
           byte[] bytes=new byte[base64Data.length()];
           int len=getBytesInternal(base64Data, bytes);
           decode(bytes,os,len);
   }
   /**
    * Decodes Base64 data into  outputstream
    *
    * @param base64Data Byte array containing Base64 data
    * @param os the outputstream
    * @throws IOException
    * @throws Base64DecodingException
    */
   public final static void decode(byte[] base64Data,
        OutputStream os) throws Base64DecodingException, IOException {
            decode(base64Data,os,-1);
   }
   protected final static void decode(byte[] base64Data,
                        OutputStream os,int len) throws Base64DecodingException, IOException {

        // remove white spaces
    if (len==-1)
       len = removeWhiteSpace(base64Data);

    if (len%FOURBYTE != 0) {
        throw new Base64DecodingException("decoding.divisible.four");
        //should be divisible by four
    }

    int      numberQuadruple    = (len/FOURBYTE );

    if (numberQuadruple == 0)
        return;

    //byte     decodedData[]      = null;
    byte     b1=0,b2=0,b3=0, b4=0;

    int i = 0;

    int dataIndex    = 0;

    //the begin
    for (i=numberQuadruple-1; i>0; i--) {
        b1 = base64Alphabet[base64Data[dataIndex++]];
        b2 = base64Alphabet[base64Data[dataIndex++]];
        b3 = base64Alphabet[base64Data[dataIndex++]];
        b4 = base64Alphabet[base64Data[dataIndex++]];
        if ( (b1==-1) ||
                (b2==-1) ||
                (b3==-1) ||
                (b4==-1) )
         throw new Base64DecodingException("decoding.general");//if found "no data" just return null



        os.write((byte)(  b1 <<2 | b2>>4 ) );
        os.write((byte)(((b2 & 0xf)<<4 ) |( (b3>>2) & 0xf) ));
        os.write( (byte)( b3<<6 | b4 ));
    }
    b1 = base64Alphabet[base64Data[dataIndex++]];
    b2 = base64Alphabet[base64Data[dataIndex++]];

    //  first last bits.
    if ((b1==-1) ||
        (b2==-1) ){
             throw new Base64DecodingException("decoding.general");//if found "no data" just return null
     }

     byte d3,d4;
     b3= base64Alphabet[d3 = base64Data[dataIndex++]];
     b4= base64Alphabet[d4 = base64Data[dataIndex++]];
     if ((b3==-1 ) ||
          (b4==-1) ) {//Check if they are PAD characters
         if (isPad( d3 ) && isPad( d4)) {               //Two PAD e.g. 3c[Pad][Pad]
             if ((b2 & 0xf) != 0)//last 4 bits should be zero
                     throw new Base64DecodingException("decoding.general");
             os.write( (byte)(  b1 <<2 | b2>>4 ) );
         } else if (!isPad( d3) && isPad(d4)) {               //One PAD  e.g. 3cQ[Pad]
             if ((b3 & 0x3 ) != 0)//last 2 bits should be zero
                     throw new Base64DecodingException("decoding.general");
             os.write( (byte)(  b1 <<2 | b2>>4 ));
             os.write( (byte)(((b2 & 0xf)<<4 ) |( (b3>>2) & 0xf) ));
         } else {
             throw new Base64DecodingException("decoding.general");//an error  like "3c[Pad]r", "3cdX", "3cXd", "3cXX" where X is non data
         }
     } else {
         //No PAD e.g 3cQl
         os.write((byte)(  b1 <<2 | b2>>4 ) );
         os.write( (byte)(((b2 & 0xf)<<4 ) |( (b3>>2) & 0xf) ));
         os.write((byte)( b3<<6 | b4 ));
     }
    return ;
   }

   /**
    * Decodes Base64 data into  outputstream
    *
    * @param is containing Base64 data
    * @param os the outputstream
    * @throws IOException
    * @throws Base64DecodingException
    */
   public final static void decode(InputStream is,
        OutputStream os) throws Base64DecodingException, IOException {
        //byte     decodedData[]      = null;
    byte     b1=0,b2=0,b3=0, b4=0;

    int index=0;
    byte []data=new byte[4];
    int read;
    //the begin
    while ((read=is.read())>0) {
        byte readed=(byte)read;
        if (isWhiteSpace(readed)) {
                continue;
        }
        if (isPad(readed)) {
            data[index++]=readed;
            if (index==3)
                data[index++]=(byte)is.read();
            break;
        }


        if ((data[index++]=readed)==-1) {
            throw new Base64DecodingException("decoding.general");//if found "no data" just return null
           }

        if (index!=4) {
                continue;
        }
        index=0;
        b1 = base64Alphabet[data[0]];
        b2 = base64Alphabet[data[1]];
        b3 = base64Alphabet[data[2]];
        b4 = base64Alphabet[data[3]];

        os.write((byte)(  b1 <<2 | b2>>4 ) );
        os.write((byte)(((b2 & 0xf)<<4 ) |( (b3>>2) & 0xf) ));
        os.write( (byte)( b3<<6 | b4 ));
    }


    byte     d1=data[0],d2=data[1],d3=data[2], d4=data[3];
    b1 = base64Alphabet[d1];
    b2 = base64Alphabet[d2];
    b3 = base64Alphabet[ d3 ];
    b4 = base64Alphabet[ d4 ];
     if ((b3==-1 ) ||
         (b4==-1) ) {//Check if they are PAD characters
         if (isPad( d3 ) && isPad( d4)) {               //Two PAD e.g. 3c[Pad][Pad]
             if ((b2 & 0xf) != 0)//last 4 bits should be zero
                     throw new Base64DecodingException("decoding.general");
             os.write( (byte)(  b1 <<2 | b2>>4 ) );
         } else if (!isPad( d3) && isPad(d4)) {               //One PAD  e.g. 3cQ[Pad]
             b3 = base64Alphabet[ d3 ];
             if ((b3 & 0x3 ) != 0)//last 2 bits should be zero
                     throw new Base64DecodingException("decoding.general");
             os.write( (byte)(  b1 <<2 | b2>>4 ));
             os.write( (byte)(((b2 & 0xf)<<4 ) |( (b3>>2) & 0xf) ));
         } else {
             throw new Base64DecodingException("decoding.general");//an error  like "3c[Pad]r", "3cdX", "3cXd", "3cXX" where X is non data
         }
     } else {
         //No PAD e.g 3cQl

         os.write((byte)(  b1 <<2 | b2>>4 ) );
         os.write( (byte)(((b2 & 0xf)<<4 ) |( (b3>>2) & 0xf) ));
         os.write((byte)( b3<<6 | b4 ));
     }

    return ;
   }
   /**
    * remove WhiteSpace from MIME containing encoded Base64 data.
    *
    * @param data  the byte array of base64 data (with WS)
    * @return      the new length
    */
   protected static final int removeWhiteSpace(byte[] data) {
       if (data == null)
           return 0;

       // count characters that's not whitespace
       int newSize = 0;
       int len = data.length;
       for (int i = 0; i < len; i++) {
           byte dataS=data[i];
           if (!isWhiteSpace(dataS))
               data[newSize++] = dataS;
       }
       return newSize;
   }
}
