content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.shiro.lang.codec;
  
  /**
   * <a href="http://en.wikipedia.org/wiki/Hexadecimal">Hexadecimal</a> encoder and decoder.
   * <p/>
   * This class was borrowed from Apache Commons Codec SVN repository (rev. {@code 560660}) with modifications
   * to enable Hex conversion without a full dependency on Commons Codec.  We didn't want to reinvent the wheel of
   * great work they've done, but also didn't want to force every Shiro user to depend on the commons-codec.jar
   * <p/>
   * As per the Apache 2.0 license, the original copyright notice and all author and copyright information have
   * remained in tact.
   *
   * @see <a href="http://en.wikipedia.org/wiki/Hexadecimal">Wikipedia: Hexadecimal</a>
   * @since 0.9
   */
  public class Hex {
  
      /**
       * Used to build output as Hex
       */
      private static final char[] DIGITS = {
              '0', '1', '2', '3', '4', '5', '6', '7',
              '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
      };
  
      /**
       * Encodes the specified byte array to a character array and then returns that character array
       * as a String.
       *
       * @param bytes the byte array to Hex-encode.
       * @return A String representation of the resultant hex-encoded char array.
       */
      public static String encodeToString(byte[] bytes) {
          char[] encodedChars = encode(bytes);
          return new String(encodedChars);
      }
  
      /**
       * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
       * The returned array will be double the length of the passed array, as it takes two characters to represent any
       * given byte.
       *
       * @param data byte[] to convert to Hex characters
       * @return A char[] containing hexadecimal characters
       */
      public static char[] encode(byte[] data) {
  
          int l = data.length;
  
          char[] out = new char[l << 1];
  
          // two characters form the hex value.
          for (int i = 0, j = 0; i < l; i++) {
              out[j++] = DIGITS[(0xF0 & data[i]) >>> 4];
              out[j++] = DIGITS[0x0F & data[i]];
          }
  
          return out;
      }
  
      /**
       * Converts an array of character bytes representing hexadecimal values into an
       * array of bytes of those same values. The returned array will be half the
       * length of the passed array, as it takes two characters to represent any
       * given byte. An exception is thrown if the passed char array has an odd
       * number of elements.
       *
       * @param array An array of character bytes containing hexadecimal digits
       * @return A byte array containing binary data decoded from
       *         the supplied byte array (representing characters).
       * @throws IllegalArgumentException Thrown if an odd number of characters is supplied
       *                                  to this function
       * @see #decode(char[])
       */
      public static byte[] decode(byte[] array) throws IllegalArgumentException {
          String s = CodecSupport.toString(array);
          return decode(s);
      }
  
      /**
       * Converts the specified Hex-encoded String into a raw byte array.  This is a
       * convenience method that merely delegates to {@link #decode(char[])} using the
       * argument's hex.toCharArray() value.
       *
       * @param hex a Hex-encoded String.
       * @return A byte array containing binary data decoded from the supplied String's char array.
       */
      public static byte[] decode(String hex) {
          return decode(hex.toCharArray());
      }
  
      /**
       * Converts an array of characters representing hexadecimal values into an
       * array of bytes of those same values. The returned array will be half the
       * length of the passed array, as it takes two characters to represent any
       * given byte. An exception is thrown if the passed char array has an odd
       * number of elements.
       *
       * @param data An array of characters containing hexadecimal digits
       * @return A byte array containing binary data decoded from
       *         the supplied char array.
       * @throws IllegalArgumentException if an odd number or illegal of characters
       *                                  is supplied
       */
      public static byte[] decode(char[] data) throws IllegalArgumentException {
  
          int len = data.length;
  
          if ((len & 0x01) != 0) {
              throw new IllegalArgumentException("Odd number of characters.");
          }
  
          byte[] out = new byte[len >> 1];
  
          // two characters form the hex value.
          for (int i = 0, j = 0; j < len; i++) {
              int f = toDigit(data[j], j) << 4;
              j++;
              f = f | toDigit(data[j], j);
              j++;
              out[i] = (byte) (f & 0xFF);
          }
  
          return out;
      }
  
      /**
       * Converts a hexadecimal character to an integer.
       *
       * @param ch    A character to convert to an integer digit
       * @param index The index of the character in the source
       * @return An integer
       * @throws IllegalArgumentException if ch is an illegal hex character
       */
      protected static int toDigit(char ch, int index) throws IllegalArgumentException {
          int digit = Character.digit(ch, 16);
          if (digit == -1) {
              throw new IllegalArgumentException("Illegal hexadecimal character " + ch + " at index " + index);
          }
          return digit;
      }
  
  
  }
  