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The source code is released under:

Apache License

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/*
 * 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
 * //from  www .  ja  v  a 2 s.  c  o m
 *      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.codec.binary;

import java.io.UnsupportedEncodingException;

import org.apache.commons.codec.CharEncoding;

/**
 * Converts hexadecimal Strings. The charset used for certain operation can be
 * set, the default is set in {@link #DEFAULT_CHARSET_NAME}
 * 
 * @since 1.1
 * @author Apache Software Foundation
 * @version $Id$
 */
public class Hex {

  /**
   * Default charset name is {@link CharEncoding#UTF_8}
   * 
   * @since 1.4
   */
  public static final String DEFAULT_CHARSET_NAME = CharEncoding.UTF_8;

  /**
   * Used to build output as Hex
   */
  private static final char[] DIGITS_LOWER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

  /**
   * Used to build output as Hex
   */
  private static final char[] DIGITS_UPPER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

  /**
   * 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 DecoderException
   *             Thrown if an odd number or illegal of characters is supplied
   */
  public static byte[] decodeHex(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 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
   *            a byte[] to convert to Hex characters
   * @return A char[] containing hexadecimal characters
   */
  public static char[] encodeHex(byte[] data) {
    return encodeHex(data, true);
  }

  /**
   * 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
   *            a byte[] to convert to Hex characters
   * @param toLowerCase
   *            <code>true</code> converts to lowercase, <code>false</code> to
   *            uppercase
   * @return A char[] containing hexadecimal characters
   * @since 1.4
   */
  public static char[] encodeHex(byte[] data, boolean toLowerCase) {
    return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
  }

  /**
   * 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
   *            a byte[] to convert to Hex characters
   * @param toDigits
   *            the output alphabet
   * @return A char[] containing hexadecimal characters
   * @since 1.4
   */
  protected static char[] encodeHex(byte[] data, char[] toDigits) {
    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++] = toDigits[(0xF0 & data[i]) >>> 4];
      out[j++] = toDigits[0x0F & data[i]];
    }
    return out;
  }

  /**
   * Converts an array of bytes into a String representing the hexadecimal
   * values of each byte in order. The returned String 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 String containing hexadecimal characters
   * @since 1.4
   */
  public static String encodeHexString(byte[] data) {
    return new String(encodeHex(data));
  }

  /**
   * 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 IllegalArgumentException {
    int digit = Character.digit(ch, 16);
    if (digit == -1) {
      throw new IllegalArgumentException("Illegal hexadecimal character " + ch + " at index " + index);
    }
    return digit;
  }

  private final String charsetName;

  /**
   * Creates a new codec with the default charset name
   * {@link #DEFAULT_CHARSET_NAME}
   */
  public Hex() {
    // use default encoding
    this.charsetName = DEFAULT_CHARSET_NAME;
  }

  /**
   * Creates a new codec with the given charset name.
   * 
   * @param csName
   *            the charset name.
   * @since 1.4
   */
  public Hex(String csName) {
    this.charsetName = csName;
  }

  /**
   * 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 DecoderException
   *             Thrown if an odd number of characters is supplied to this
   *             function
   * @see #decodeHex(char[])
   */
  public byte[] decode(byte[] array) throws UnsupportedEncodingException {
    return decodeHex(new String(array, getCharsetName()).toCharArray());
  }

  /**
   * Converts a String or 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 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
   *            hexadecimal 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 ClassCastException {
    char[] charArray = object instanceof String ? ((String) object).toCharArray() : (char[]) object;
    return decodeHex(charArray);
  }

  /**
   * Converts an array of bytes into an array of bytes for the 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.
   * <p>
   * The conversion from hexadecimal characters to the returned bytes is
   * performed with the charset named by {@link #getCharsetName()}.
   * </p>
   * 
   * @param array
   *            a byte[] to convert to Hex characters
   * @return A byte[] containing the bytes of the hexadecimal characters
   * @throws IllegalStateException
   *             if the charsetName is invalid. This API throws
   *             {@link IllegalStateException} instead of
   *             {@link UnsupportedEncodingException} for backward
   *             compatibility.
   * @see #encodeHex(byte[])
   */
  public byte[] encode(byte[] array) {
    return StringUtils.getBytesUnchecked(encodeHexString(array), getCharsetName());
  }

  /**
   * Converts a String or 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 String or array, as it
   * takes two characters to represent any given byte.
   * <p>
   * The conversion from hexadecimal characters to bytes to be encoded to
   * performed with the charset named by {@link #getCharsetName()}.
   * </p>
   * 
   * @param object
   *            a String, or byte[] to convert to Hex characters
   * @return A char[] containing hexadecimal characters
   * @throws EncoderException
   *             Thrown if the given object is not a String or byte[]
   * @see #encodeHex(byte[])
   */
  public Object encode(Object object) throws ClassCastException, UnsupportedEncodingException {
    byte[] byteArray = object instanceof String ? ((String) object).getBytes(getCharsetName()) : (byte[]) object;
    return encodeHex(byteArray);
  }

  /**
   * Gets the charset name.
   * 
   * @return the charset name.
   * @since 1.4
   */
  public String getCharsetName() {
    return this.charsetName;
  }

  /**
   * Returns a string representation of the object, which includes the charset
   * name.
   * 
   * @return a string representation of the object.
   */
  @Override
  public String toString() {
    return super.toString() + "[charsetName=" + this.charsetName + "]";
  }
}

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