Helper class to provide Base64 encoding routines. : Base64 « Development Class « Java

1. Java
2. Development Class
3. Base64

Helper class to provide Base64 encoding routines.

      
/*******************************************************************************
 * Copyright (C) 2006 Google Inc.
 * 
 * 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.
 ******************************************************************************/


/**
 * Helper class to provide Base64 encoding routines.
 * 
 * @author ? - added by ksim
 * @date March 6th, 2007
 * @version 1.0
 * @todo Not unit tested yet.
 */

/**
 * The <b>Base64Coder</b> class provides methods for encoding strings and byte
 * arrays into Base64 format. It also provides methods for decoding
 * Base64-encoded strings and character arrays.
 * 
 * @version 1.0 beta
 */
public class Base64Coder {

  private 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;
    }
  }

  /**
   * The <b>encode (String s)</b> method encodes a string into Base64 format.
   * No blanks or line breaks are inserted.
   * 
   * @param s
   *            The string to be encoded.
   * @return String in Base64-encoded format.
   */
  public static String encode(String s) {
    return new String(encode(s.getBytes()));
  }

  /**
   * The <b>encode (byte[] in)</b> method 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 containing the Base64-encoded data.
   */
  public static char[] encode(byte[] in) {
    int iLen = in.length;
    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;
  }

  /**
   * The <b>decode (String s)</b> method decodes a Base64-encoded string.
   * 
   * @param s
   *            The Base64 String to be decoded.
   * @return A String containing the decoded data.
   * @throws IllegalArgumentException
   *             if the input is not valid Base64-encoded data.
   */
  public static String decode(String s) {
    return new String(decode(s.toCharArray()));
  }

  /**
   * The <b>decode (char[] in)</b> method decodes an array of Base64-encoded
   * characters. 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.");

    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.");
      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.");
      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;
  }
}

   
    
    
    
    
    
  

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