/*

  * 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.codec.binary;

 import java.nio.charset.Charset;

 import org.apache.commons.codec.BinaryDecoder;

 import org.apache.commons.codec.BinaryEncoder;

 import org.apache.commons.codec.CharEncoding;

 import org.apache.commons.codec.Charsets;

 import org.apache.commons.codec.DecoderException;

 import org.apache.commons.codec.EncoderException;

 /**

  * Converts hexadecimal Strings. The charset used for certain operation can be set, the default is set in

  * {@link #DEFAULT_CHARSET_NAME}

  *

  * This class is thread-safe.

  *

  * @since 1.1

  * @version $Id$

  */

 public class Hex implements BinaryEncoder, BinaryDecoder {

     /**

      * Default charset name is {@link Charsets#UTF_8}

      *

      * @since 1.7

      */

     public static final Charset DEFAULT_CHARSET = Charsets.UTF_8;

     /**

      * 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(final char[] data) throws DecoderException {

         final int len = data.length;

         if ((len & 0x01) != 0) {

             throw new DecoderException("Odd number of characters.");

         }

         final 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(final 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} converts to lowercase, {@code false} to uppercase

      * @return A char[] containing hexadecimal characters

      * @since 1.4

      */

     public static char[] encodeHex(final byte[] data, final 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(final byte[] data, final char[] toDigits) {

         final int l = data.length;

         final 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(final 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(final char ch, final int index) throws DecoderException {

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

         if (digit == -1) {

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

         }

         return digit;

     }

     private final Charset charset;

     /**

      * Creates a new codec with the default charset name {@link #DEFAULT_CHARSET}

      */

     public Hex() {

         // use default encoding

         this.charset = DEFAULT_CHARSET;

     }

     /**

      * Creates a new codec with the given Charset.

      *

      * @param charset

      *            the charset.

      * @since 1.7

      */

     public Hex(final Charset charset) {

         this.charset = charset;

     }

     /**

      * Creates a new codec with the given charset name.

      *

      * @param charsetName

      *            the charset name.

      * @throws java.nio.charset.UnsupportedCharsetException

      *             If the named charset is unavailable

      * @since 1.4

      * @since 1.7 throws UnsupportedCharsetException if the named charset is unavailable

      */

     public Hex(final String charsetName) {

         this(Charset.forName(charsetName));

     }

     /**

      * 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[])

      */

     @Override

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

         return decodeHex(new String(array, getCharset()).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[])

      */

     @Override

     public Object decode(final Object object) throws DecoderException {

         try {

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

             return decodeHex(charArray);

         } catch (final ClassCastException e) {

             throw new DecoderException(e.getMessage(), e);

         }

     }

     /**

      * 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 #getCharset()}.

      * </p>

      *

      * @param array

      *            a byte[] to convert to Hex characters

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

      * @since 1.7 No longer throws IllegalStateException if the charsetName is invalid.

      * @see #encodeHex(byte[])

      */

     @Override

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

         return encodeHexString(array).getBytes(this.getCharset());

     }

     /**

      * 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 #getCharset()}.

      * </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[])

      */

     @Override

     public Object encode(final Object object) throws EncoderException {

         try {

             final byte[] byteArray = object instanceof String ?

                                    ((String) object).getBytes(this.getCharset()) : (byte[]) object;

             return encodeHex(byteArray);

         } catch (final ClassCastException e) {

             throw new EncoderException(e.getMessage(), e);

         }

     }

     /**

      * Gets the charset.

      *

      * @return the charset.

      * @since 1.7

      */

     public Charset getCharset() {

         return this.charset;

     }

     /**

      * Gets the charset name.

      *

      * @return the charset name.

      * @since 1.4

      */

     public String getCharsetName() {

         return this.charset.name();

     }

     /**

      * 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.charset + "]";

     }

 }