Encode and decode data in Base64 format as described in RFC 1521 : Base64 « Development Class « Java

1. Java
2. Development Class
3. Base64

Encode and decode data in Base64 format as described in RFC 1521

      
/**************************************************************************
 *
 * A Base64 Encoder/Decoder.
 *
 * This class is used to encode and decode data in Base64 format
 * as described in RFC 1521.
 *
 * <p>
 * Copyright 2003: Christian d'Heureuse, Inventec Informatik AG, Switzerland.<br>
 * License: This is "Open Source" software and released under the <a href="http://www.gnu.org/licenses/lgpl.html" target="_top">GNU/LGPL</a> license.
 * It is provided "as is" without warranty of any kind. Please contact the author for other licensing arrangements.<br>
 * Home page: <a href="http://www.source-code.biz" target="_top">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.
 *
 **************************************************************************/


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 string into Base64 format.
   * No blanks or line breaks are inserted.
   * @param s  a String to be encoded.
   * @return   A String with the Base64 encoded data.
   */
  public static String encode(String s) {
    return new String(encode(s.getBytes()));
  }

  /**
   * 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) {
    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;
  }

  /**
   * Decodes a Base64 string.
   * @param s  a 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()));
  }

  /**
   * Decodes Base64 data.
   * 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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