/*

  * 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.commons.id;

 import org.apache.commons.id.DecoderException;

 import org.apache.commons.id.EncoderException;

 /**

  * Hex encoder and decoder.

  * 

  * @since 1.1

  * @author Apache Software Foundation

  * @version $Id: Hex.java 480488 2006-11-29 08:57:26Z bayard $

  */

 public class Hex {//implements BinaryEncoder, BinaryDecoder {

     /** 

      * 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'

     };

     /**

      * Converts an array of characters representing hexidecimal 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 hexidecimal digits

      * @return A byte array containing binary data decoded from

      *         the supplied char array.

      * @throws DecoderException Thrown if an odd number or illegal of characters 

      *         is supplied

      */

     public static byte[] decodeHex(char[] data) throws DecoderException {

         int len = data.length;

         if ((len & 0x01) != 0) {

             throw new DecoderException("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 DecoderException Thrown if ch is an illegal hex character

      */

     protected static int toDigit(char ch, int index) throws DecoderException {

         int digit = Character.digit(ch, 16);

         if (digit == -1) {

             throw new DecoderException("Illegal hexadecimal charcter " + ch + " at index " + index);

         }

         return digit;

     }

     /**

      * Converts an array of bytes into an array of characters representing the hexidecimal 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

      *                  a byte[] to convert to Hex characters

      * @return A char[] containing hexidecimal characters

      */

     public static char[] encodeHex(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 hexidecimal 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 hexidecimal digits

      * @return A byte array containing binary data decoded from

      *         the supplied byte array (representing characters).

      * @throws DecoderException Thrown if an odd number of characters is supplied

      *                   to this function

      * @see #decodeHex(char[])

      */

         public byte[] decode(byte[] array) throws DecoderException {

                 return decodeHex(new String(array).toCharArray());

         }

     /**

      * Converts a String or an array of character bytes representing hexidecimal values into an

      * array of bytes of those same values. The returned array will be half the

      * length of the passed String or 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 object A String or, an array of character bytes containing hexidecimal digits

      * @return A byte array containing binary data decoded from

      *         the supplied byte array (representing characters).

      * @throws DecoderException Thrown if an odd number of characters is supplied

      *                   to this function or the object is not a String or char[]

      * @see #decodeHex(char[])

      */

         public Object decode(Object object) throws DecoderException {

                 try {

             char[] charArray = object instanceof String ? ((String) object).toCharArray() : (char[]) object;

                     return decodeHex(charArray);

                 } catch (ClassCastException e) {

                     throw new DecoderException(e.getMessage());

                 }

         }

     /**

      * Converts an array of bytes into an array of bytes for the characters representing the

      * hexidecimal 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 array a byte[] to convert to Hex characters

      * @return A byte[] containing the bytes of the hexidecimal characters

      * @see #encodeHex(byte[])

      */

         public byte[] encode(byte[] array) {

                 return new String(encodeHex(array)).getBytes();

         }

     /**

      * Converts a String or an array of bytes into an array of characters representing the

      * hexidecimal values of each byte in order. The returned array will be

      * double the length of the passed String or array, as it takes two characters to

      * represent any given byte.

      *

      * @param object a String, or byte[] to convert to Hex characters

      * @return A char[] containing hexidecimal characters

      * @throws EncoderException Thrown if the given object is not a String or byte[]

      * @see #encodeHex(byte[])

      */

         public Object encode(Object object) throws EncoderException {        

                 try {

             byte[] byteArray = object instanceof String ? ((String) object).getBytes() : (byte[]) object;

                         return encodeHex(byteArray);

                 } catch (ClassCastException e) {

                         throw new EncoderException(e.getMessage());

                 }

         }

 }