Implementation of MIME's Base64 encoding and decoding conversions. : Base64 « Development Class « Java






Implementation of MIME's Base64 encoding and decoding conversions.

      
/*
 * 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.
 *
 */

public class Base64 {
  /**
   * Implementation of MIME's Base64 encoding and decoding conversions.
   * Optimized code. (raw version taken from oreilly.jonathan.util, and
   * currently org.apache.xerces.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 org.apache.xml.security.transforms.implementations.TransformBase64Decode
   */

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

  /**
   * Field _base64length
   */
  static int _base64length = Base64.BASE64DEFAULTLENGTH;

  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] = '/';

  }

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

  /**
   * Encode a byte array and fold lines at the standard 76th character.
   * 
   * @param binaryData
   *          <code>byte[]<code> to be base64 encoded
   * @return the <code>String<code> with encoded data
   */
  public static String encode(byte[] binaryData) {
    return encode(binaryData, BASE64DEFAULTLENGTH, false);
  }

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

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

  /**
   * 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 String encode(byte[] binaryData, int length, boolean wrap) {

    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[];

    encodedData = new char[(numberQuartet * 4) + (wrap ? numberLines : 0)];

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

    int encodedIndex = 0;
    int dataIndex = 0;
    int tripletsDone = 0;
    for (int line = 0; line < numberLines; line++) {
      for (int quartet = 0; quartet < quartesPerLine; 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];

        tripletsDone++;
      }
      if (wrap) {
        encodedData[encodedIndex++] = 0xa;
      }
    }

    for (; tripletsDone < numberTriplets; tripletsDone++) {
      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;
    }
    return new String(encodedData);
  }

  /**
   * Decodes Base64 data into octects
   * 
   * @param encoded
   *          String containing Base64 data
   * @return Array containing decoded data.
   */
  public static byte[] decode(String encoded) throws RuntimeException {
    byte[] base64Data = encoded.getBytes();
    // remove white spaces
    int len = removeWhiteSpace(base64Data);

    if (len % FOURBYTE != 0) {
      throw new RuntimeException("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 RuntimeException("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 RuntimeException("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 RuntimeException("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 RuntimeException("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 RuntimeException("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;
  }

  /**
   * remove WhiteSpace from MIME containing encoded Base64 data.
   * 
   * @param data
   *          the byte array of base64 data (with WS)
   * @return the new length
   */
  protected static 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;
  }

  /**
   * @param args
   */
  public static void main(String[] args) {
    // TODO Auto-generated method stub

  }
}

   
    
    
    
    
    
  








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